Could be the basis for an interesting Democrat-wank timeline.
I'm not sure further changes to the Presidency would affect Obama much at all; even under the best-case scenario you're talking about adding MO (+11 EV), MT (+3 EV) and GA (+15 EV); that would give Obama/Biden 394 EV to McCain/Lieberman's 144, which isn't materially different than OTL. There just isn't much room, structurally, for Obama to win much more than he did in OTL.
However, you've got two pretty close races in the Senate that the Democrats lost in 2008 -- Saxby Chambliss (R) over Jim Martin (D) in Georgia by 3%, 49.8-46.8, and Mitch McConnell (R) over Bruce Lunsford (D) in Kentucky, 53-47.
As I suggested earlier, with a bad VP pick by McCain, it's pretty easy to envision Obama's coattails (and a suppressed Republican turnout) getting Jim Martin the extra 3.2% he needs to clear the 50% threshold in Georgia and win the Senate race without a runoff. It's a lot harder to envision Lunsford making up six points in Kentucky (where Obama got crushed), but a truly apathetic Republican base might be enough to do it.
In the House, the Democrats won 21 seats in 2008. Depress Republican turnout by 6%, and you add 16 Dem pickups. Most of these are just padding -- in Alaska-AL (Ethan Berkowitz over Don Young, CA-3 (Bill Durston over Dan Lungren), CA-44 (Bill Hedrick over Ken Calvert), CA-50 (Nick Leibham over Brian Bilbray), FL-25 (Joe Garcia over Mario Diaz-Balart), IL-10 (Daniel Seals over Mark Kirk), KS-2 (Nancy Boyda holds her seat against Lynn Jenkins), KY-2 (David Boswell over Brett Guthrie), LA-2 (Bill Jefferson holds his seat over Joseph Cao), LA-4 (Paul Carmouche over John Fleming), MO-9 (Judy Baker over Blaine Luetkemeyer), NE-2 (Jim Esch over Lee Terry), PA-6 (Bob Roggio over Jim Gerlach), and SC-1 (Linda Ketner over Henry Brown, Jr.), for example.
But there are two significant long-term effects here. In WA-8, Daily Kos fave Darcy Burner defeats Dave Reichert and becomes the voice of the Congressional Progressive Caucus.
And, of course, the most significant of them all: in Minnesota's 6th district, Elwyn Tinklenberg defeats freshman incumbent Michele Bachmann. (OTL, Bachmann won by just 3% in 2008.)
So there you have it: a perfect Dem-wank. Obama wins a landslide, gets a filibuster-proof majority and then some in the Senate, 61-39, a 273-162 majority in the House, and trades a feisty firebrand of the extreme right (Michele Bachmann) for a feisty firebrand of the extreme left (Darcy Burner).