Somehow, google deleted my previous post on how to act for this election
So here:
The Senate is also important, so Actblue is place you can donate.
Swing Left has a virtual phone bank you can participate in (and some other ways like donations etc).
Resistance Labs is where you can text to get out the vote.
Vote Forward is a way to do postcards to help improve voter turnout.
Princeton Election Consortium has a list of races where your money will make the most difference. They have Senate races by "power" (where your money goes the furthest). And one for redistricting, if you're interested.
Of course this doesn't mean that our work is over even if the Dems win (there will still be work to do), but it's a good first step. Let me know if I've missed something.