Look into GnuPG. It's probably the best consumer level encryption and it's free. Takes a while to get the hang of http://macgpg.sourceforge.net/
You can also try Puzzle Palace http://personalpages.tds.net/~brian_hill/puzzlepalace.html
If you're using Microsoft Word, you can put passwords on your file. (That's what I use for my journal entries. )
For Microsoft Word: When you have the doc open, go to Preferences and down to Security on the left side. From there you can put in a Password to Open and then a Password to Modify.
Bingo! God, I love this forum.
By the way, I'm going to try the disk utility program also, so thanks for the tips everyone. Do I just go on System Preferences?