In keeping with our desire for models I thought a handy hyperlinked list of suitable 6mm stuff might be handy. So here is a few ranges, feel free to add more underneath, I can update this list and if its of any use maybe it can be pinned.
So
GW Epic.
GW FW. Yes, getting cheaper relative to GW every day! )
FW Aeronautica. Yes I still think its not 6mm!
15mm.co.uk. No personal experience, are those infantry too tall? Experience to the contary suggests "6mm Crusaders as Tau Firewarrior proxies." And expert opinion says they are 9mm, which is about what they look!
Adler. Again no personal experience, is it 6mm? the infantry look a touch large.
Brigade. Some nice stuff.
C in C. Yes, they do a very few sci fi bits as well.
Command horizon. Likewise.
DRM. More excellent stuff.
Dream pod Nine, mostly the wrong size but some stuff link the little chaps at the link might be good.
Exodus wars. No more need be said.
Force XXI miniatures.
Fortress Figures. No longer openly for sale, but if you email the chap he can still make them. Prices range from $0.50 to $1.
Graviton Warrior. A new addition.
Game Figures Inc. A range of aliens and terrain at the moment.
Ground Zero Games. The Big One. For many UK 6mm sci fi gamers these chaps were the first and certainly the biggest range for a very long time.
Hall of ancient warriors. Who are these chaps? From a search on the net.
Ironfist They aren't GW models, honest
But are a new range of super heavies for 6mm.Ironwind. A bit too 10mm even for Epic? Some think not.
Irregular - yes, they do 6mm too. No doubt in the same style as their other ranges. I
can't bring myself to buy any to find out though. I quote from below "suitable for a high contrast impressionistic painting technique."
MAATAC. Originally released by 'superior', know nothing about them.
Ogre. The vehicles work, the infantry is too big.
Majic minitures. Currently UFO centric but with more in the works.
Old Crow. Did these used to be Ainsty stuff?
Plasma blast games, some details int he announcement thread hopefully.
Reapers CAV has stuff which many people have used successfully, especially for Navy assets.
Reaver from Tac-Com has done a fair bit as well.
Reiver Casting is relatively undetailed focusing on armour, but some potential for civilian vehicles or L&D transports?
Reviresco. The 'days of empire' range. Pretty poor I feel but odd ad mech vehicles maybe.
Scotia stuff. Only ever seen this stuff at shows.
Sues Little Bits. Early reports put them at nearer 9mm.
W.i.l.d.fire robot spiders with guns.
ZandrisIV Miniatures, anime style ogre miniatures alternatives, as well as Homeworld ships and other models.
Buck Rogers gun pods as recommended by Javelin here.
Konami. Out of production Eagle Transports from Space 1999 are fantastic. You have to search for them though!
GHQ The best for 6mm vehicles (well even a bit smaller than 6mm potentially depending on how you judge the scale of 1:285!).
Navwar. Ok not sci fi, but still a useful place to browse if you want to spend all your money and can drop by the shop. In fact a useful prompt for other 6mm stuff to come in!
Armorcast is doing 6mm terrain
Game Craft Minitures mostly terrain.
Mainly Military Sci FI buildings.
Snapdragon. Now OOP.
Big Time !! 
