Jermareo Davidson should be available at the #34 or even #50. Sometimes cited for lack of effort, but he's got a wide array of post moves on the offensive end, and defensively, he's a terrific shot blocker. If we're really going to try and fulfill our need for a post player through the draft (as there don't seem to be any good ones available through free agency), though, we should really set our sights on Glen Davis out of LSU. Some have him going late first round, some have him falling all the way to the middle of the second round. If he's available, I don't think there's anyway we can pass him up. Another option would be drafting Pau Gasol's younger brother, Marc Gasol, who may or may not be available at #34. Don't know much about him, but reading a couple of articles, he seems to be similar to his brother, but the consensus seems to be that he will not make as much noise in the NBA as Pau has.
If we're looking for a point guard, our options include Taureen Green (who made a ton of noise at the Pre-Draft Camp, and because of how well he did, may not be available) or Jared Jordan (SI had a great article on him, I think it's posted in this thread somewhere), among others.
If we're looking to move Buck this summer, which we may have to in order to make salaries match in some sort of trade involving other players, we may want to take a good look at DJ Strawberry, especially with Devean George leaving. He's likely to go un-drafted, but with no real needs that we absolutely need to fill, we might as well grab a hard-nosed defender like Strawberry with the last pick of the 07 draft. He improved his stock plenty at the Pre-Draft Camp, with a very strong showing, so he may actually be drafted towards the end of the second round, and surely will have suitors if he goes undrafted.
The only player I've read the Mavs are taking a good look at is Adam Halulska, the only player they currently have a workout scheduled with. He's a shooting guard with plenty of range, a bit inefficient though, looking at stats from his last year at Iowa.
I really feel like our best chance to improve through the draft is to draft Big Baby out of LSU. Here's a good video on the dude:
http://youtube.com/watch?v=p2xARh4_dfs