Yes, databases are legal. Tablebases and engines are illegal.
Are chess databases legal to use?

yes you may as the previous poster wrote. Here is a link to the rules
http://support.chess.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=711&nav=0

Please note, this only applies to Online (turn-based, correspondance style, slow play, what ever you want to call it) Chess. For Live Chess, no outside help is allowed. Period.

Can one get advice from other people?
I'm not talking grandmasters here, it's just I like to discuss chess with my dad. Since I'm currently at college, he hasn't given me any advice on my games here, as it is hard to do so over the phone, but as I have two weeks of school left before I head back for summer vacation, and it probably will come up.
Are we allowed to discuss on-going chess games with others? This may, or may not result in me playing a different move than I would have. I know there would be no way to tell, but I would still like to remain honorable while playing.

Can one get advice from other people?
I'm not talking grandmasters here, it's just I like to discuss chess with my dad. Since I'm currently at college, he hasn't given me any advice on my games here, as it is hard to do so over the phone, but as I have two weeks of school left before I head back for summer vacation, and it probably will come up.
Are we allowed to discuss on-going chess games with others? This may, or may not result in me playing a different move than I would have. I know there would be no way to tell, but I would still like to remain honorable while playing.
It is possible (I believe, although I'm not the authority) to discuss your games with out your dad telling you what moves to make and what strategy to use.
YOU: He's got my kingside tied up in knots!
YOUR DAD: Why'd you let him do that?
YOU: Well I ...bla bla bla
At least that's how it would go with my dad.
But really don't let anyone tell you what move to make. That's cheating.

No. It's been made clear to me that we are not allowed to discuss our current games with anyone other than the opponent.

Here is a simple presentation of the rules:
Resource |
What is it? |
Is it permitted DURING Turn-Based (and Vote Chess) play? |
Is it permitted DURING LiveChess play? |
Asking another person for advice |
Includes discussing a game-in-progress in the chess.com Forums |
NO* (except during VoteChess - when discussion WITHIN the team is expected) |
NO |
Books |
This is a static resource and involves no calculation of best move. |
YES |
NO |
Chess Engine(chess computer) the move evaluator within e.g. Fritz, ChessMaster, etc. |
Software (or free-standing gadget) that calculates the best move from a given position |
NO (except by agreement of both players, where specifically arranged and must be UNRATED games e.g. in a tournament created for that purpose) |
NO |
Conditional Moves (Pre-Moves) |
Setting your response in advance to one or more of your opponent’s moves |
YES |
YES |
Internet articles; Google searches |
This is a static resource and involves no calculation of best move. |
YES |
NO |
Games Database e.g. chess.com’s Game Explorer |
A database (or collection) of previous games, that is searchable. (It is most useful as an Opening Database - although forVote Chess games, the Explore button takes you directly into Game Explorer at that position). |
YES* (There is some debate about whether DBs containing engine-engine games are permitted). |
NO |
Separate board for analysis e.g. chess.com’sAnalysis Board |
|
YES |
NO |
TableBases (Endings Database) |
The results from an analysis of end games (stored in a database) in which the sequence of moves to achieve the best outcome has been calculated |
NO |
NO |
v2

@Artfizz:
It's a good table... here's a question... regarding tablebases... we understand it's completely illegal to calculate one's specific ending moves with a tablebase. We also understand it's legal to consult training materials. So suppose I'm faced with N and B vs K ending, and I don't know how to accomplish the mate.
Can I train myself to perform the mate using printed matter, or a youtube video? Surely.
Can I train myself (during the game) to perform the mate using a chess engine? a tablebase? I'm inclined to say, yes -- but you're on your honor... you really have to be learning the mate, not using the engine or tablebase to find a move for your specific position. This gets a bit dicey however, if the engine or tablebase passes thru the position you're in.

Hmm, thanks for the info.
I must admit, I was unaware that you were not allowed to use another board during Live Chess, I have a small travel board that I normally use when I play online chess.
Not that I play live chess really at all, as it continually times out on me, (and yes, I'm using Firefox. I'm pretty sure it has to do with the proxy server my college has up).

Can one get advice from other people?
I'm not talking grandmasters here, it's just I like to discuss chess with my dad. Since I'm currently at college, he hasn't given me any advice on my games here, as it is hard to do so over the phone, but as I have two weeks of school left before I head back for summer vacation, and it probably will come up.
Are we allowed to discuss on-going chess games with others? This may, or may not result in me playing a different move than I would have. I know there would be no way to tell, but I would still like to remain honorable while playing.
It is possible (I believe, although I'm not the authority) to discuss your games with out your dad telling you what moves to make and what strategy to use.
YOU: He's got my kingside tied up in knots!
YOUR DAD: Why'd you let him do that?
YOU: Well I ...bla bla bla
At least that's how it would go with my dad.
But really don't let anyone tell you what move to make. That's cheating.
My dad took third place in Alabama when he was around my age, and though his chess skills have seriously deteriorated since then, he can't look at a chess board without... thinking out loud, as it were.

artfizz that was a great table u prepared which is supposed to close the subject...i supp it should be available somewhere for easy access to those who ask the same question again...can u put it in a form of link or something

@Artfizz:
It's a good table... here's a question... regarding tablebases... we understand it's completely illegal to calculate one's specific ending moves with a tablebase. We also understand it's legal to consult training materials. So suppose I'm faced with N and B vs K ending, and I don't know how to accomplish the mate.
Can I train myself to perform the mate using printed matter, or a youtube video? Surely.
Can I train myself (during the game) to perform the mate using a chess engine? a tablebase? I'm inclined to say, yes -- but you're on your honor... you really have to be learning the mate, not using the engine or tablebase to find a move for your specific position. This gets a bit dicey however, if the engine or tablebase passes thru the position you're in.
One for the chess.com lawyers!
"Are you running an engine in connection with this game?" (I don't mean you, personally). If 'yes', then you're on dodgy ground. Suppose you've now assimilated the K vs. K+3B ending: you can steer the game towards that particular endgame. The engine has been of material assistance during a specific game.

artfizz that was a great table u prepared which is supposed to close the subject...i supp it should be available somewhere for easy access to those who ask the same question again...can u put it in a form of link or something
http://www.chess.com/article/view/site-playing-rules-a-guide-for-the-perplexed
I have read somewhere here at chess.com that it is legal to use the internet or books in online games to be able to play book opening moves. Is it really? Because that looks like cheating to me :S
I'm sorry if this is something I should know or something that has been asked before but it just annoys me that I don't know the answer.