The undisclosed pick involved in yesterday's trade between the Lions and Seahawks for Lawrence Jackson has been revealed as a sixth-rounder in 2011. Because the Lions had two sixth-round picks in the 2011 draft (they got one from Philadelphia for trading away the 220th pick of the 2010 draft), it's unclear if the Seahawks got the Lions' pick or the one formerly belonging to the Eagles.
Some other moves involving 2011 picks that have been made include the trade that sent Kevin O'Connell to the Jets and the trades that brought Chris Houston and Shaun Hill to Detroit. In the O'Connell deal, the Lions got a seventh-round pick in 2011, and they sent one to San Francisco to get Hill. For Houston, one of the things traded to Atlanta was a conditional seventh-round pick in 2011, so the Lions technically will only lose it if the conditions involved with the pick (e.g. certain amount of games played) are met.