Larry Sabato and his crystal ball currently predicts a 32 seat gain in the House for the GOP and a 7 gain seat gain in the Senate.
http://www.centerforpolitics.org/crystalball/Sabato's background
Wikipedia: "In August 2006, Crystal Ball predicted that the Democrats would gain 29 seats in the House of Representatives and 6 seats in the Senate, providing them with a majority in both chambers. Sabato's predictions proved correct: each of his 33 Senate predictions were accurate, and in the House, Democrats gained 29 seats on election night, the precise total predicted by the Crystal Ball (Democrats would go on to pick up a 30th seat in the December 12, 2006 run-off in Texas' 23rd district).<9>
In July 2008, Crystal Ball correctly projected that Barack Obama would win the presidency in a near-landslide.<10> Sabato predicted a 364-174 margin in the Electoral College, as well as the popular vote percentages.<11> The prediction was merely one point off the mark, with the actual result on November 4, 2008 being Obama 365 and McCain 173. Crystal Ball also accurately predicted 100% of all 35 Senate races, and 11 gubernatorial races correctly.<12>
In 2006 Sabato was named the most accurate prognosticator by FOX News, MSNBC, CNBC, and Pew's Project for Excellence in Journalism. In 2006, Sabato was the only national analyst to correctly predict the exact Democratic gains in Senate and House contests."
http://en.wikipedia.org/wiki/Larry_Sabato