OK here goes
If you want the best of the best go to to GHQ they are expensive but the detail is fantastic
www.ghq.com
Next up would be CinC miniatures not sure of the website but the quality is nearly as good as GHQ
Scotia Models do a fair range, some are good some are awful mind you
There is also Armstrong minis that do some oddities that no one else covers
there is also Sytrex and Navwar..some of these are good some again are bad
If all else fails have a look at this website
http://www.microarmormayhem.com/