Give money to Obama now
Now would be a good time to give money to Obama's campaign. One of my favorite things about Obama's campaign is that it is funded mainly by small donors. This makes him less beholden to narrow moneyed interests, and it also lets him spend more time campaigning and less time schmoozing for dollars.
Giving money early in a campaign is so much more productive than giving later in the campaign. Late money just goes into ad buys that aren't terribly useful; people are sick of ads by then. Early money goes to build campaign infrastructure, hire staff, do planning, and generate buzz. Your dollar will go much further now than later in the campaign.
I would also point out that there are other progressive candidates who need money. ActBlue is a good place to find them. Obama's going to get a lot of money, and there are other races that are important, too.