At the moment, liquid cooled processors aren't really practical - Fans work fine unless you're specifically lookinig for a silent system. I believe ASUS makes several very high quality liquid-cooled systems, but I have my doubts about the integrity of the liquid resiviors - I'll stick with fans until I move to a quad-core processor. My fan-cooled dual core 3 GHZ works fine for now
*EDIT*
Gel cooling isn't something I've heard of... the only gel I know of that has any sort of cooling capacity is that gel between the processor and heatsink. I can't imagine a gel being useful for cooling the entire processor simply because you'd need something that circulates (like water or oil)... Oil would actually be better because it doesn't conduct electricity, but I don't think anyone's using oil-based coolant....yet.