Whether you're thinking of going freelance, or are freelancing already, there is a site that is an awesome resource, FreelanceSwitch.com. It really is a must read! It doesn't matter if you're just a freelancer hopping around to different studios like me, or if you're running your own full business from home, there is so much advice to pick through. I've only recently started reading it, and not only has it opened my eyes to new ideas, but it has also helped me to put words to things I already knew worked, but didn't fully understand why.
Check it out, and subscribe to it in your feed reader! It's the single best resource dedicated to freelancing that I've seen.
(Thanks to Kevin Williams, and his awesome Google Reader shared items, for pointing me to this fantastic website!)