Site of the Week or two...archive      
orangebikes.com
Orange have been a respected player on the world stage as long as I've been riding, from their days of all-steel ranges and custom componentry to the more sensible and competitive approach they have today. The 2002 ranges is the best we've seen from them; still some cracking steel frames but their expertise in aluminium continues apace and the value for money and choice is amazing. They're also still British and now provide Steve Peat with his ride. The site is great, so whatever your mtb bag is, make it your business to check it out!
dirtyhabit.co.uk
I remember dirty habit coming onto the scene a few years ago. I saw their t-shirts in a magazine and bought a couple, something I just hadn't done before. The fresh designs, including the dh icon- my personal Best Logo In Mountain BIking™- have always stood out, so as a place to buy their stuff dirtyhabit.co.uk is a great site.
However, the best thing about it is that it shows how much they are riders first and a business second. The shop section is great, but it's maybe one tenth of the site. The forums, news, links and all the other stuff give as good an idea of the people involved as the designs.
It's nice to see people who love mountain biking involved in the business side. There are oters, but the dh site really shows it.