Check this site out:
http://protools.cjb.net/
This is where some of the hackers get their file cracking tools from, but it also seems to have a lot of file packers/encryptors that you might find usefull in making your games harder to crack.
I can recommed upx for good compression, not sure how secure it is though...

Most people use UPX (http://upx.sourceforge.net/) for real-time exe packing. It works great, and it's free.

However, there are a few older virus scanners that will flag these exe files as infected. This can cause support problems and a problem with any site that allows user reviews, like download.com.

It's a shame, because these packers are really cool...