The Particletree Guide to Starting Your Business
Published December 20th, 2005 edit replace rm!
Particletree have written a good quick guide to the paperwork part of starting a business. It has generally good advice and pointers for more.
My only real comment is that most bootstrappers should only really start worrying about these things, when they are doing real business.
Their advice is for creative freelancers and they would generally tend to get into real business straight away. The same is true for any other freelancers such as IT Consultants/Contractors.
However when starting your web or software startup where there is real ramp up time, wait until you are seeing real steady income for incorporating, tax, legal etc advice. It is much more important to spend your energy and money on building your business. The only exception for this is if you want to take deductions against other income (eg. salary).