NEPatriotsDraft.com has become a good resources for tracking rookie free-agent signings in recent years.
They're stringing together reported contract agreements and signings.
These are not official lists, but an NFL team official I spoke with said the list for his team was accurate. The teams will make announcements once the deals are in place, at which time a little more analysis will be in order. As undrafted free agents, however, these players are long shots by definition.
According to Elias Sports Bureau, 57 undrafted rookies opened the 2010 regular season on 53-man rosters. That was up from 37 in 2009, 33 in 2008, 40 in 2007 and 36 in 2006.
One name to add: The Seahawks did reach agreement with quarterback Zac Lee, as ESPN's Adam Schefter reported. That gives Seattle two undrafted quarterbacks, plus Charlie Whitehurst, heading into initial camp practices.