The Detroit Lions' official site reported that Auburn defensive tackle Nick Fairley and Pittsburgh wide receiver Jonathan Baldwin visited the team on Wednesday. It's unlikely that Fairley will fall to the Lions, but they are doing their homework just in case. Baldwin, on the other hand, could be someone they look at if he's available in the second round.
National Football Post reported on these visits as well. Also, they mentioned that LSU running back Stevan Ridley and Virginia Union offensive tackle David Mims visited the Lions on Wednesday. It was reported before that Mims was going to work out with the Lions, and since neither of their visits were mentioned on the team's official site, I'm guessing that's what they were in town for -- a workout.
Another reason I believe they were in town for a workout is because some local players mentioned on Twitter and Facebook that they worked out with the Lions on Wednesday. Michigan tight end Martell Webb tweeted about his workout, as did Michigan State wide receiver Mark Dell. Michigan defensive back James Rogers mentioned his workout with the Lions on Facebook, so I'm guessing quite a few guys worked out with them on Wednesday.
The NFL Draft visit tracker has been updated to reflect all of this news.
UPDATE: National Football Post also reported earlier this week that Georgia wide receiver Kris Durham has visited the Detroit Lions. Like with Ridley and Mims, I'm guessing it was a private workout rather than an actual visit.
UPDATE II: Ball State defensive end Robert Eddins also worked out for the Lions on Wednesday.