Help changing standard sounds/adding more?

[ndriver182]

I've been getting much more comfortable using OSX since I made my final switch to OSX in January. One thing though that I have noticed about OSX is that there seem to be a lot less sounds (or at least less ways to change them) than what I was used to with WinXP. I'm looking for suggestions on changing sounds. I found an application called Bleep Blop and installed it, but it doesn't seem to have a complete listing of sounds to change. Are there any other programs that do the same sort of thing? Any suggestions are definitely welcome.