Freshmeat
Then search for imlib... I'm 99.9999% positive you'll get an exact match. That site and
Sourceforge are your best friends for finding software (maybe even rpmfind.net if you like RPMs).
You are warned though: Imlib has dependencies. To install it, you'll probably have to install other packages (like libjpeg). If you use a package manager like RPM or apt, then it should take care of the dependencies for you. If you like compiling from source, then you'll have to plod through them yourself.