As you can see, lots of campaigns are following Chandler's lead and advertising on Daily Kos and other blogs.
Stephen just did a ranking of the top 30 races in his mind. I'll be doing my own list for OurCongress.org. Jerome is going to restart MyDD in a few weeks, and he'll likely have his own list.
Some of the candidates who are advertising will be on one or more of those lists, some will not. It doesn't matter, because House races can be very fluid. There's no way anyone would've predicted that GA12 would go GOP in 2002. Things happen to upend the best, most intelligent long-term predictions.
While competitive districts (like GA12) are no-brainers -- our small-dollar donations can also go far in making safe- or lean-GOP districts competitive. And the DCCC won't fund such races unless the Democratic candidate shows the ability to raise money on his or her own. So by lending a hand to such candidates, you are also increasing the chances that they'll be able to score bigger bucks from the national party. Not to mention money begets money. The more money comes in, the easier it is for the candidate to raise it (it makes him or her more "viable").
And even if our guys don't win, helping make safe- or lean-GOP seats more competitive forces the Republicans to spend money defending territory, rather than attacking our own incumbents. So such investments can pay off in several ways.
One final note -- the campaigns advertising on the blogs are also doing their part to build a strong and vibrant progressive blogosphere. By donating to those campaigns you're also helping fund your favorite bloggers. Double goodness all around.
That's not to turn our backs on the also-important Senate races. We actually have a greater chance of taking the Senate than we do the House. And given that only a handful of those races are competitive, OK, AK, NC, SC, FL, LA, and SD (I think IL and GA will switch parties with little effort) -- there's a lot of good we can do by targeting those races financially and via volunteer efforts.