Three dollars and some change

The first three were the ones I was going to suggest. :-) Also have a look at Tassos's fanfiction.net page - s/he has an enchanting in-progress Atlantis/Farscape cross (http://www.fanfiction.net/s/2683551/1/) (warning: there's a cute kid) and a completed SG1/Farscape cross, "Pathways" (http://www.fanfiction.net/s/1345146/1/).

Ummm... author "acs" on TTH has a series of Dawn-centred drabbles that cross Highlander and SG1. http://www.tthfanfic.com/Story-7732/acs+And+Death+did+not+stop.htm

Marcus Rowland (on TTH) wrote "The Key to Byzantium", which I seem to recall I enjoyed. http://www.tthfanfic.com/Story-5220/MarcusRowland+The+Key+to+Byzantium.htm. Basically, the tattoo'ed dead monks and warriors from GloryWar get temporarily mistaken for dead Jaffa.

There was a Voyager/SG1 crossover I read a while back, but don't recall much about except for Paris and O'Neil trading a movie reference. I enjoyed it despite the non-congruent universes.