A good book on the subject is Modern Chess Miniatures by Neil McDonald. It's full of GM blunders and how to avoid (or spot) these opportunities.
Chess is all just pattern recognition. When you see the same old thing again and again, it starts to sink in. Unfortunately, it takes the cruel hand of experience to teach us.
Your not a computer you will make blunders. It worrying when they are simple misses.
I often make them: I believe it is the intensity of the game especially when you are winning. You take it for granted that you will not fail to see your queen is under threat and then you miss it.
We play to win but computers just play by the rules they have no feelings.
All good advice above.
One thing that I have done that has helped avoid blunders is to recognize when you are most likely to make them. For me (and it sounds like for a lot of players), it happens most when I think I have a winning attack combination. I've blundered enough times in these situations that I've learned to run through two quick checklists before making my move:
1. PFCC -- pins, forks, checks and captures (read this somewhere, forget where). I run through this list before the move, checking to see if my opponent has any of them.
2. Before moving to a square, I check each of the eight directions that the square could be attacked from (two vertical, two horizontal, and four diagonal), PLUS a check for any nearby knights. Make sure to find all the possible attacks on the destination square before moving to it. This helps especially if you are prone to missing long-range attacks, like I am.
Good luck!
One thing that I've fallen victim to many times: premature attack elation. My girlfriend says I'm not pronouncing correctly...
Already good advice given, and you seem to understand the problem anyway yourself :)
I just want to add that it gets to be a habit and becomes easier the more you practice blunder checking so don't be afraid to put in some hard work over the board :) When you're finally ready to make your move (after all the usual considering and calculating) "sit on your hands" and do one last blunder check. Forget everything you just looked at and imagine only the move you planned to make. Now treat that imagined position as a tactical puzzle with your opponent on the move... can he win anything? If not then go ahead and play the move.
At first this may seem like you're spending a lot of energy at the board checking every single move... but it becomes natural and easier and certainly the main payoff is less blunders!
Well! play more. One of my programming professors said "practice makes perfect".
Thanks to you all. Glad I've provoked a good discussion. Good news is that probably the most important game this year has just been won, no blunders in sight! 
It was not classic blunders that we talked about. It was about great looking attacking moves that are instant loss.
But when we talk about classic blunders, I tried to eliminate them from my live chess games, pay just a little bit more attention, and play safe, I rocketed my self from 1600 to 1800 on chesscube in 2 weeks.
I know a sure-fire way to avoid blunders. Fischer did a really good job using this technique from 1975-1992.
Don't play chess!
Haha,Fezzik. I know an even better way- resign on move 1!Jk, just look at the board carefully and learn from crazy blunders. Yesterday I was bored out of my mind, and I lost to an 100 rated guy!