I do a lot of work in SecondLife and Real Life for that matter with marketing literature and product design. Sometimes you just don't have any ideas on where to begin with a particular project. I find it helpfull at that stage to look at other people's work for inspiration (not thievery, just inspiration ... well mostly anyway). I find that a clipart resource is one of the best ways to get that kick start. Lately, I find myself enamored by a little open source project called OpenClipart at:
This project, faintly associated with Inkscape, has 6900+ vector (SVG) drawings. These SVG drawings can be used in conjunction with Inkscape or the Gimp to complement any projects that you may be working on.
Another great resource for these kinds of projects is IStockPhoto. They take submissions from the community and you pay a dollar per image. These images are royalty free as well (with some restrictions). IStockPhoto in conjunction with the OpenClipart project and Inkscape brings the means to create brilliant marketing presentations to the masses on a budget. What could be better than that? Oh, that's right, sliced bread.