http://downloads.guru3d.com/
I have found lots of utilities and modified drivers there. I haven't used any of them as I like to stick with official drivers and stock speeds. I like my computer running as compatible as possible.
I have tried other drivers and teaks as well but have had some display and compatibility related problems here and there using them. Of course, using tweak utilities requires trial and error to make them work properly, that is the fun part and when it works the results are great.
It's just that I'm lazy and lack the time to try hundreds of combinations to squeeze more performance from my card.