Count me as someone who wants some typing in the REST world, based on the arguments made in the post by Aristotle Pagaltzis last week.
We're talking about contracts here. Contracts need to be formalized, somehow. English is not the best language to use, especially since we have much more precise languages available to us.
My thoughts here are really just an extension to my thoughts on data serialization. Services are just the next level of thing that need to be meta-described.
Several folks have pointed out WADL (Web Application Description Language) as a potential answer, but it has at least one hole: it doesn't have a way of describing non-XML data used as input or output. For example, JSON. It certainly is simpler and more direct than WSDL, so it does have that going for it.
All in all, good thoughts all around, but we have more work to do, more proof to provide. And by more work, I don't mean getting a handful of experts in a smoky back room mandating what the formats are going to be. In fact, I'm not so sure we need a single 'format'. If you've creating some kind of machine-readable schema to describe your data and your services, you're way ahead of the game.
In any case, don't wait for WADL to be finshed before starting to build out schema for your services. Use WADL if you can, use something else (hopefully simpler) if it's more appropriate for you.