Have you thought, wow, I really miss SGA and wish I had an excuse to watch it again?
Either way, sga_rewind is for you! It's a standard rewatch community, just launching now, so you have time to get involved. The current plan is to start discussion of the first episode, "Rising (Part 1)", beginning this coming Saturday, August 29. (Rather than having everyone watch at a certain time, folks are encouraged to watch whenever their schedule permits.) New episode discussions will start weekly.
I'm helping with organization, at least to get things started. I'll start each discussion post with a brief summary and with links to transcripts, for those who don't have access to the episodes but still want to participate. I'll also be encouraging folk to post links to episode-related fanworks. I will keep discussions open for at least a week. (It's LJ, so it's not like there's a feasible way to close discussions cleanly, but in terms of setting expectations: active discussions for one week. Posts will be around for those who want to join a bit late and catch up.)
(ETA: Waiting for the full series box set? Amazon says it releases October 6. They also presently list it at $170 as the pre-order discount; for reference, they're asking $97 for the first four seasons and $22.50 for season five -- so, you can save a good $50 by getting the individual seasons instead. I have no idea what special features the box set will include; the studio doesn't seem to be saying yet. If you do want to wait, I'm trying to draw up a catch-up scheme, since the comm will be only six-seven episodes in by that point, so if you're willing to tackle the first several episodes at two per week to catch up, you can still play.)