I use HIARCS Chess Explorer. This is not free, but is by far the best chess program available for Mac.
Personal Game Database Program for Mac?
HIARCS Chess Explorer is the best commercial chess program on the Mac by far. I help develop the free open source program ChessX which is very similar but with fewer features. It doesn't have nearly as many features as SCID but IMO has a much nicer user interface.

What are the key features it's missing in your opinion? Thanks for making a free alternative possible.
I hate the SCID user interface. It doesn't even have a continously resizable game board. Not only that but none of the fixed sizes are big enough. ChessX has a very attractive game board that you can make the size that you want.
Chessbase is like flying an experimental aircraft. Sure it has tons of nice features, but it doesn't make you want to use it when it crashes all the time.
I have used Hiarcs Chess Explorer on a Mac for a few weeks now and it is definitely better than Chessbase. Chess Explorer is faster searching than Chessbase (yes I have that on my PC) and Explorer is much more stable.
I can agree with the other posters that Chessbase crashes all the time and even corrupts my databases so much so I had to back up my database before every change in CB.
Chess Explorer by contrast has been running here for some weeks without any issues. It is very easy to use and I also received a free update yesterday with some more great features for preparation that even Chessbase does not have.
Finally the Mac has the best chess software and I am very happy with Hiarcs Chess Explorer.

I went w/ HIARCS and it's definitely the best I've seen so far, but far from perfect. Exploring the top games is bogus - I'm looking to make a move and see the percentages and the games (like chess.com's), but instead it creates a variation on whatever game's selected.
I was able to make moves and view the moves, stats and games in the explorer window. In topgames db what I did was start a new game and follow the moves in the opening explorer, I have the show games locked so I can view the moves available in the current position and all the games played with this position. It records the moves and variation in the notation so it is easy to see where I am in the variations and quickly go to another line. I think that makes it excellent since it records my work. Chessbase has a similar feature which also creates variations but it is much, much slower finding games and CB lacks some features in this area that Explorer has...
When I want to look at a particular game I save the variation (that is my work after all!) and look at the game in question. It was then I found an incredible feature in Chess Explorer, I can copy the game I am interested in and MERGE it back into my analysis game - that is incredibly useful for preparation and analysis. Bravo team Hiarcs!

Thanks Morphy. Really excited to try your solution - hope I can easily replicate it. A bit hard to follow - not your fault necessarily, just tricky HIARCS vocab.

I find Hiarcs is awesome. I wanted a back up online version in case of computer problems. It's a 8 month old Mac, so the problems should be a while off. Just in case though, I upload my games to 365chess.com. The free version of 365 is not very beneficial for me, but to upgrade is only $10 a year (donation, give more if you choose). Very efficient and inexpensive!
I want to find a database program to input my games and opening lines into. Right now I'm using Scid, which is ok - and it's free - but it's not user-friendly and has issues. I've seen PC users with infinitely better programs - I'm looking for a strong counterpart.
Any ideas?