Both great links on taxes. I've personally not thrown myself into that area of study enough, but as for general business links, here are a few I've stuck on my website.
A list of definitions covering author's rights
http://www.scribendi.com/advice/writers_know_your_rights.en.htmlPreditors and editors- great resource for checking out legitimate agents and editors
http://www.anotherealm.com/prededitors/Backspace...a general collection of links and info on the industry
http://www.bksp.org/SFWA page covering all aspects of the business and contracts
http://www.sfwa.org/contracts/Also, to avoid the nasty side of the business, check out Writer, Beware, where people devote their precious time uncovering and prosecuting scamming agents and publishing houses. They also dedicate a decent portion to the writing biz itself.
http://www.sfwa.org/beware/I hope this is some of what you're looking for.