I really like Arena 3.5. It is free, open source software, and better than most paid software.
To enter games, you have to click the “edit” button located on the lower right. I had to read the help file to figure that out, but it’s REALLY easy. Once you click on EDIT, you can enter moves, save them, and email the PGN file, or do whatever you want.
Also when downloading the software, make sure to download Arena 3.5 SETUP, the 2nd link on the download page. I made the mistake of downloading the Arena Zip file (I just assumed that the top link was the best one to download - silly mistake).
Just a tip: Use Arena, then consider buying ChessBase only if you have entered 100 games into Arena or other free software. People who get ChessBase too early just kind of ruin their ChessBase experience, in my opinion.
Also iPad/iPhone users should use Stockfish to enter and email games. This is a lot simpler than anything else, and it is free. I recommend StockFish over a lot of paid apps (Stockfish is currently free, and it is also an open source project).
I don’t usually prefer free stuff… I believe it is good to pay for quality chess software. When it comes to finding software for entering games, there is basically the free stuff, and the expensive stuff, and the stuff in between isn’t very good.
Mac Users: Download the free Stockfish app from the App store. It’s in its early stages of development, but it does a good job of entering/saving games.