This Fall Could Be A Sea Change
That's important. It means there's a decent chance we'll finally put a check on the Bush administration, perhaps even start some investigations. If things go well it will mean building a national progressive consensus around key issues. Health Care will get another shot if we can put together two winning cycles in a row (e.g. gain ground this fall and then take either the White House or Congress in '08).
My advice for you? Get savvy on your representatives. This fall's action is going to be faught in over four-hundred 500,000-person districts. It's going to mean a lot of local nuance, which is where grassroots participation can make the biggest impact. There's also probably some important action at the state/county/city level. The best strategy here is to flood the zone; to push forward on every front and juice turnout as much as possible. At the very least get registered and vote Democrat in the fall, and try to get your friends to do the same. If you're on board for the slow-steady takeover of the government (e.g. you really want that Health Care, out of Iraq, etc), then find a campaign (even a long-shot) and get directly involved.
Getting involved is actually doubly important. It's necessary if the change is to happen, and should Dems indeed put together a comeback with our help, they're going to start getting more and more of that corporate slush money. HMOs, Big Pharma, and the Insurance Rackets all give to the GOP about 2-to-1, but that ratio will probably change if there's a transfer of power. People power will be critical in keeping 'em honest.