TBH, most of the apps I've tried don't work as well as I'd like. Trickster MOD has a fast charge setting but doesn't work well otherwise. ROM Toolbox works nicely, except that it doesn't have an easy way to toggle fast charge (you can enter "ffc" into its terminal emulator, but it's not very convenient). Kernel Tuner does have a fast charge setting, but I don't recommend using it to set frequencies or letting it apply settings on boot.
Edit: tested Trickster a little more thoroughly and am not as impressed as I was. I'll have to try to figure out why it's acting strangely, since I really like it otherwise.
Edit 2: newest 3.4 builds have several fixes that improve support for Trickster. Overclocking, undervolting, and toggling minimum voltage are all supported. I like Trickster more than the other apps I've tried, so I'll try to support it whenever possible.