Recently I poped up on one promising project - called Socium Trade. They are on starting basis now, as far as I understood the project is about to launch in November, you may want to take a look at it. Find it here on Bitcoin Forum.

The feature I like that they offer the traders profiles, where you can find a trader for yourself. Though Im not sure from which minimum you can start, but looks like there will be possibility to have a joint investment pools for that cases.