I tried to find the filming schedule, but I haven't found it so far. The first day of filming was on June 18 (
link/
link), and I've read that 22 episodes were ordered on a
link.
On
link and
link the 3 first episodes of season 7 is listed, with episode titles and airing dates(14 September 2009,21 September 2009,???), although I'm not sure whether that's confirmed by The CW or not.
Sorry I couldn't find a filming schedule, but to get some updates on season 7 I guess it's a good idea to check out
link/
link once in a while, or check out
link and
link on twitter.