The Lions made a trade on Saturday and four moves on Sunday that were not confirmed until earlier today.
The trade, which sent Alphonso Smith to Denver in exchange for Dan Gronkowski, also involves draft picks. The picks involved are undisclosed, but the Lions' release stated that the two teams "swapped" selections in the 2011 draft. Whether or not that means they simply swapped picks in one round or something along those lines is unclear, but picks changed hands in this trade.
The other moves confirmed today involve the release of Rocky Boiman and Dennis Northcutt and the addition of Stefan Logan and Spencer Havner. The interesting thing about Havner is that he is listed as a linebacker rather than a tight end. Originally it looked like he would play tight end for the Lions, just as he did last year with the Packers, but instead it appears his main position will be linebacker. When he entered the league a few years ago, Havner was a linebacker.