[CentOS] installing progs from source on CentOS

I'd like to install NagiosQL on CentOS, but I don't see a yum package 
for it, so I'm going to download the source code.

If I download it, where in CentOS's file system (i.e. in which 
directory) is the best place to untar, compile, and run it?

(Sorry, I've been spoiled by packages!)