I’ve been a frequent user of OpenTable the past year or so, but the missing scenario has always been making reservations on the go.  They have finally launches their mobile site:

Avoid the hassle of calling around for a restaurant reservation or the panic of securing a last-minute table. With OpenTable Mobile, you can find a restaurant, choose an available table, and book your reservation - right on your mobile phone.

Check it out on your mobile phone at http://mobile.opentable.com/.