What more can I say - some of the most inspiring stuff on the web. For a complete listing check out http://www.gijoelinks.com, but for eclectic and inspiring you'd be hard pressed to beat....
These are the ones I find myself visiting again and again, they have links on their sites too, so using these you'll become familiar with some amazing stuff out there.
Francis Tavares Battlefields - the first time I showed this page to a friend who isn't into this hobby he said 'Oh My God - I never realised...'. Sums it up nicely. Action City used to sell his stuff and I'm lucky enough to have one of the uniforms - but I still want the rest of them...............
JimBob Wan's Image Depot - the guru of plastic surgery in the 1/6th scale ! Does inspiring work with a Dremel !
Mark Cole - Was customising and selling stuff years before the market became popular again.
Ransome Chua - wonderful photos, details and German camo too.
Some on-line sellers I have used and would reccommend
Farout Toys - When I visited some family on the West Coast I dropped in to Armando Bravo's shop in San Jose, he was most a kind and helpful person, when I can I will buy here.
JusticeFighters - For small parts, bodies and a wonderful selection.
Good Stuff to Go - Some hard to find and old stuff - great selection and a great service.
Voyager Toys - I have a certain nostalgia about this one because it was the first shop I ordered from.
Eklyps - the extremely helpful Greg Brown - some great custom stuff (e.g. Brian Vota) and a mass order for Cotswold Collectibles as well.