With the 1st pick of the 2009 NFL Draft the Detroit Lions select:
1.01-QB Matthew Stafford-Georgia
Detroit is obviously rebuilding, and they have been weak at QB for as long as I've been alive(really going back to Layne) they saw what a difference Matt Ryan and Joe Flacco made and will hope Stafford can make a similar impact in what is a wide open division.
Many Lions fans will be hoping for an O-lineman here, but I believe a QB makes more sense. This is an extremely deep draft for O-lineman and Detroit has 2 other picks in the top-33. There should be a quality O-line prospect available at one of those picks, they likely won't be a quality QB prospect available at those picks, hell, Stafford might be the only really good prospect at QB this year.
Watching Stafford in college, he kind of reminds me of Carson Palmer, and with Calvin Johnson and Kevin Smith in place, the Lions will be pretty set at the skill positions for some time with this pick.
I considered Crabtree(who I think is the best player in this draft) but I believe Detroit is very aware of what the reaction would be if they took another top-10 WR.
ETA: I don't think there is a defensive player worthy of this pick. I believe the Lions may be a player for Matt Cassel, but since there are no trades allowed, Stafford is the choice.