Some of my favourite links for 6mm stuff:
Buidings and scenery
Great buildings and scenery
Total Battle Miniatures
My personal favourite buildings
Great range of buildings ect. from all periods. Best Napoleonic range around.
World War Scenics
Great range of static grass etc.
Realistic Modelling Services
Probably the best range of different flocks including odd types like Poppy Field
Ebay seller of good everyday wargaming trees
Nice range of cheap wargaming trees for everday battling
4D Model Making Materials
Great custom made trees in all sizes for that special occasion for a diorama for instance, not cheap but great looking stuff
Arcane Scenery and Models
Good range of products including all the Javis flocks
Perfect Six Scenics
Rare 300th scale items like barrels and barricades
Precision Wargames supplies Ltd.
Nice thin metal bases in many different sizes or custom sizes
The best and most detailed 6mm figs available
Full range of 6mm figs and even some flag sheets
Free downloads for most of the Napoleonic units, great resource
March Attack by Crusader Publishing
Not tried them yet but they look very good after reading through
Perfect Six 6mm Figure Painting
Probably the best 6mm Napoleonic painter in the UK
10/12mm WW2 and 6mm Napoleonic gaming
Great Napoleonic/WW2/basing etc
A guy in New Zealand, very good scratch built terrain and scenery
Perfect Six Forum
Dedicated brand new 6mm forum
The Miniatures Page
A mine of information on all periods and scales but prone to a lot of threads ending up in a slanging match for some reason!
Fantastic little static grass applicator
Great hand-made brushes (UK)
Rosemary and Co
I only use the best pure Kolinsky Sable brushes and these are very good.
I recommend the series 33, 323, and 441 for figure painting (depending on purpose).
Use the Ivory Short Flats range for dry brushing (bases and terrain).