IN-8, John Hostettler ® vs. Brad Ellsworth (D): Incumbent Hostettler has been doomed by double-digits most of the season, so if he manages a low-single-digit loss (or, unbelievably, a win), that bodes ill.
IN-2, Chris Chocola ® vs. Joe Donnelly (D): Incumbent Chocola is a poster boy for the more policy-oriented sins of his party, being a loyal Republican whoÃ's supported tax cuts and big oil and so on; his district is relatively conservative. He's lagged slightly in the polls, but if he loses big, that may be a harbinger of an anti-Republican sweep.
IN-9, Michael Sodrel ® vs. Baron Hill (D): Sodrel has polled the closest to his challenger of these three endangered Republican incumbents, and this is the real bellwether race in Indiana. If he pulls off a comfortable win, scale back your optimism for other toss-ups.
IN-3, Mark Souder ® vs. Tom Hayhurst (D): Nobody really thinks Souder will lose, so if he topples, that looks real real good.
I'll see where I can steal some Kentucky info from, polls close at 6 there too.
UPDATE From commenter Tilthouse:
KY-02: This is the last minute long shot. If we win here, the wave is VERY big and we are taking the Senate too.
KY-04: This one has been on the radar for a long time. Rematch between Davis ® and former Congressman Lucas (D), who is well liked (and VERY conservative -- well, it's a VERY conservative district). The PVI is R+11 (!). The polls have gone back and forth but mostly have the R ahead recently.
KY-03: A perennial race to watch, since this district is notionally Democratic. But incumbent Anne Northrup ® has a reputation for being a good politician and has does her contituency work well. However, challenger Yarmuth (D) is polling ahead now in tight single digits.
My analysis of KY-04 & KY-03 is that the conventional wisdom (that KY-04 is more vulnerable than KY-03) is wrong. If we win both, we have a solid wave (30+ seats). If we win one, it's still looking good. If we get KY-03 but not KY-04, the races were successfully nationalized. If we get KY-04, the pundits are basically on target.