Ben Hall has posted a nice summary of the Parameterized Test Features in NUnit 2.5 Alpha-3. Of course, being from the UK and all, he calls them "Parameterised" Tests.
Some of the new features are similar to approaches taken in mbUnit, about which Ben has written in past blogs. As it happens, those posts were often the best - and sometimes only - source of information I could find on how those features ought to work. So thanks for the cross-pollination you provide, Ben!