If I do hourly rate, I also charged about $80 an hour for new stuff, and then support depends on the circumstance. If it's something wrong with code I've written (a bug I missed), it's generally free. If I haven't written it and it needs fixing, or nothing is wrong but the client wants to change something, like resize the layout then I charge between 40 and 80 an hour depending on the extent of the project.
For some clients I offer a per project flat rate, but I might stop doing that since I have run into a few clients that complain that stuff like changing the layout, restructuring the site, or other time consuming jobs should be included in the price even though they have already accepted the final product and these are new modifications. And most of the time it's quicker just to do the changes than hassle with the client.