USB Key Encryption: How?

I downloaded and installed TrueCrypt on my Mac for the purpose of keeping all of my files encrypted, but it seems that you have to install TrueCrypt on every computer you wish to mount the drive on (besides using the portable windows truecrypt).

Does anyone else use TrueCrypt? Is there any way around this sort of annoying requirement? Are there any viable, user-friendly alternatives to encrypting a USB key’s contents? Any help is great. :)