Election Predictions lists the following take-over seats:
AZ-8 D-Gabrielle Giffords v. R-Randy Graf (Jim Kolbe)
CO-7 D-Ed Perlmutter v. R-Rick O'Donnell (Bob Beauprez)
CT-2 D-Joseph Courtney v. R-Rob Simmons (inc)
FL-16 D-Timothy Mahoney v. R-Mark Foley (inc)
IA-1 D-Bruce Braley v. R-Mike Whalen (Jim Nussle)
IN-2 D-Joseph Donnelly v. R-Chris Chocola (inc)
IN-8 D-Brad Ellsworth v. R-John Hostettler (inc)
IN-9 D-Baron Hill v. R-Mike Sodrel (inc)
KY-4 D-Ken Lucas v. R-Geoff Davis (inc)
NC-11 D-Heath Shuler v. R-Charles Taylor (inc)
NY-24 D-Michael Acuri v. R-Raymond Meier (Sherry Boehlert)
OH-18 D-Zach Space v. R-Joy Padgett (Robert Ney)
PA-6 D-Lois Murphy v. R-Jim Gerlach (inc)
VA-2 D-Phil Kellam v. R-Thelma Drake (inc)
VT-AL D-Peter Welch v. R-Martha Rainville (Bernie Sanders)
TX-22 D-Nick Lampson v. R-Tom DeLay (inc)
Of course, one is Sanders' seat. But this puts the House at D-219 to R-216.
Many races are very tight and many Dems are polling ahead of the Repuke opponents, so we should expect that the list will grow before November, especially with this Foley business.
Not a single Dem held seat is in serious jeopardy at this time. What's even better is that we have all the momentum. Watch things to start really jumping our way in the last month as the majority of undecideds break our way. This could be a huge turnover of power.
BTW, another poster is correct, GOTV is the way to victory.