http://en.gogloom.com/Unitedti/omnimaga/

this is like google, but it search for IRC channels on the web, it's pretty cool for finding channels about stuff you like and it even show stats (even though not really accurate, for example Omnimaga max users online is 26, while the stats show 22), and you can also view what channels are on a network, even though it only show the most active ones.