Just in case you weren't aware, SB Nation has a blog that is dedicated to everything NFL Draft, and it is called (quite ironically) Mocking The Draft. They've rounded up contributors from all of SB Nation's NFL team blogs to participate in a Community Mock Draft of the first two rounds that will go right up until the actual draft in April.
For the Denver pick, they went to John Bena of Mile High Report, and he chose Texas A&M linebacker Von Miller. Bena explains the pick:
Linebacker is another huge position of need for the Broncos, and a position synonymous with Broncos football. I wanted the Broncos to get Rolando McClain in 2010, but the Raiders were able to grab him first. This year, the Broncos can get that impact linebacker and should take advantage of the opportunity. Miller would instantly inject athleticism onto a team that needs it, and with the Broncos going back to the 4-3 defense, they have need at the position. A group of D.J. Williams, Miller and Mario Haggan (or Wesley Woodyard) would be an upgrade - especially with Elvis Dumervil and Robert Ayers moving back to defensive end.
Mocking The Draft contributor Dan Kadar reacts:
After coming from a rush linebacker/defensive end position, he may not make an immediate all-around impact in a 4-3 scheme. He may start out as a situational player, and that might not be the best usage of the second overall pick. Dareus, though, would fit right into Denver's defense and can easily play three downs. While there is depth at defensive line this year, none of that depth possesses Dareus' talent.
This is a little bit higher than Miller has been projected to go, and as Kadar points out, he isn't the best fit for the Broncos scheme. Miller might have enough talent to justify being taken second overall, but that doesn't mean the Broncos should necessarily draft him there.