I don't really use bookmarks on AO3 myself, but I like it when other people use them so I can find cool stories :) Maybe I should start using them as a rec list equivalent.

As for places to find SGA recs, when I first came into SGA fandom I was lucky and found many long rec lists, on LJ but also on people's own websites. I think several might have been taken down by now, but if you want I can check if I still have a few links.