I frequently take small personal commissions, generally on a monthly basis. The best place to be alerted for openings at this time is my Twitter account, @aspen_eyes. For current offerings and prices, see this document.
I take larger commissions and freelance work on a case-by-case basis, and rates will vary depending on complexity, and whether the commission is for personal use (I retain the copyright and the work is not used for profit) or commercial use, or somewhere in between. For inquiries about these it is best to contact me directly via email at email@example.com.