I don't know why people are dancing around this issue. I'll name some dollar amounts for you. As a LAMP consultant, I charged $100/hr. USD take-home and worked W-2. I'm now looking to get into independent (non-W2) consulting and will be charging from $50-$100/hr. USD on a sliding scale based on the type of work and the ability of the client to pay. Not all small businesses can pony up $100/hr., but mid-to-large corporate clients certainly can. Database tuning gigs can see $250-$300+ hr., but that's a very specialized skill set. You'll need to determine the going rate for your market and start out in the middle of it. If you go to low, you sell yourself short and look cheap (which can sometimes give the illusion of poor quality). If you aim too high, you price yourself out of the market.
Good luck!