I get far far less of this kind of thing than I imagine Kos does (very little, in fact, which is fine by me), but the best way for candidates to reach out to the netroots now is to begin by reaching out to local bloggers. No matter how much research I do I can't possibly have any decent sense of the 470 odd federal races that will happen in '06. More importantly, local races require local press and as we've seen local press will pay attention to local blogs in these kinds of things.
The real value of the netroots to campaigns won't really be, for the most part, their ability to raise money. Sure, campaigns are always trying to get donations from anywhere they can and I can certainly understand that. I'm happy to suggest candidates for the Eschaton community to support. But, an email or phone call from a campaign manager isn't going to do squat to encourage me to do that.
The buzz about campaigns, and the "infiltrating" into the netroots, is for the most part going to come from the ground up now. Reach out to local bloggers.