ludditerobot is organising the 'Scatterlings and Orphanages' Africander ficathon - there are still a few countries left to be claimed, it would be beyond cool if the whole continent was covered so go sign up!
jpublic is organising a Rewind/Reboot challenge for the girls of Buffy & Angel! Details are here
naol is still running the masterlist for the BtVS/AtS 70 questions fic challenge (and I will get the site updated tonight, I swear!) Go, pick a character and join the madness (characters already written are fair game by the way!)
bellatemple is organising the Firefly/Serenity version of the 70 questions challenge - go here and sign up!
naol is looking for interest in a 'fics for graphics' -athon. Go - take a look!
And, last - but not least! shannon730 is looking for sign-ups for joss_las Round Two!
Wow - that's a lot of challenges!
ETA I've updated the 70 Questions for... site with all the profiles listed on the masterlist over at naol's journal.