Jimenez I thought would be a decent player too, but his 219 average is ugly to say the least. Right now I'm not touching him. Cintron is another guy who showed some pop and had SS eligibility, which I thought made him a valuable commodity, but he has been a fairly big disappointment as well. I had him at my SS position in lieu of Reyes, but have since dropped him, first for Adam Everett, and now I'm using Juan Uribe, who isn't playing today
As for the two pitchers you mentioned, I'd like to think that Santana will get it together and have a very strong season, but so far he hasn't looked particularly good. Same for Contreras, except I expect a little less of him. In any case, I'd hang on to both. They could be effective producers in the near future.
As for sleepers at 2B/SS, man, they're hard to come by right now. At 2B, you have Ronnie Belliard, who's good, but has no power, Marlon Anderson and Keith Ginter, who aren't full time, all of which might be taken anyway. Matt Kata might deserve a look. He's got upside, and is a decent run producer, and MAY even show a little pop a little ways downt the road.
As for SS it really isn't much better...Adam Everett, Royce Clayton, Omar Vizquel, Pokey Reese, take your pick, you're not going to get much here.
Jose Valentin MIGHT be available if you have a league of impatient owners, and if you can stomach his career average of around 240, then he'll supply you with some occasional pop.
In any case, with both positions, it's a very shallow talent pool.