It's seldom that I go shopping for furniture, so links only get added here when I buy something, after searching around the net for a good deal. If you have some recommendations on links that I should append, please email chinnery@ocf.berkeley.edu.

Walmart, Target, and IKEA are fairly good for purchasing household items cheaply.

Making your own furniture
Ashby Lumber, at 824 Ashby Avenue in Berkeley, is good for buying wood if you're making your own furniture.

Bean bags
Bean bags are, in my opinion, the ultimate seat for comfort. Hailing from the seventies, you can still find them commonly in Australia and New Zealand. The best place I've found in the USA for buying bean bags, with a great warranty of seven years (most places offer one year) and an inner bag so that you can wash the outside (very necessary - you spill things on your favourite love seat occasionally!) is BeanBagFurniture.