A few weeks back Kickstarter’s Cineskates project funded with almost half a million from backers.
It was only a matter of time till someone came up with a budget friendly solution. Instructables user fungus amungus built a similar contraption using a Hybrid Gorillapod and $35 worth of Rollerblade wheels (for two sets of dollies).
For this project you actually have to drill the Gorillapod unlike the click-based Cineskates system, but saving about a $100 may provide some incentive.
[Tripod Dolly on instructables]