I just saw a link to the Multiverse pairings leftover list on lizamanynames' LJ and am strangely tempted even though I wouldn't get a story myself. For you Blake's 7 writers out there, these are still up for grabs:
4. Mele-On Grayza (Farscape) / Servalan (Blake's 7)It might be fun, especially as there are no minimum length requirements, ratings restrictions, or time limits on these. Also you can ignore the slash or ampersand and write whatever rating you like; there's an encouraging lack of rules. I rather fancy numbers 39 and 49 myself.
12. Roj Blake (Blake's 7) & Farscape
26. Odo (Star Trek: Deep Space 9) / Cally (Blake's 7)
31. Bialar Crais (Farscape) / Travis (Blake's 7)
39. Kerr Avon (Blake's 7) / Data (Star Trek: The Next Generation)
40. Servalan (Blake's 7) / Saffron (Firefly)
49. Jean-Luc Picard (Star Trek: The Next Generation) & Blake's 7
72. Leela (Dr. Who) / Cally (Blake's 7)
82. Kira Nerys (Star Trek: Deep Space 9) / Kerr Avon (Blake's 7)
91. Cally (Blake's 7) / Daniel Jackson (Stargate SG-1)
Oh and if you're not into B7, there are 100 requests so your fandom's almost sure to be there. Not that I'm sure where you send the stories to...
[Edit] andrastewhite's running it and I've asked her for details on posting. I've taken 49, entropy_house has taken 39, and executrix 12.
And I now have more details. The Multiverse 2004 page is here and you can contact andrastewhite on andraste (at) bigpond (dot) com to claim a request, and that's also where you sent the story.