We use the Petmate Deluxe Fresh Flow Cat water fountain for our three cats. One of them would drink from the sink and sometimes the toilet, and this has pretty much stopped him. He actually drinks from the top of the water flow, the other two drink from the bowl.
Pros: Good flow, holds a lot of water, cats like it, $43 on Amazon
Cons: Kind of loud when water is low, has a filter but can still get mildewy and needs to be washed
We just bought a second one for downstairs, and we've had the first over 10 years and it still works great.