Diagram Designer is a free, easy-to-use flowchart program
One solid option is MeeSoft's Diagram Designer. It's extremely easy to get started with: select an element from the sidebar, drag it onto your workspace, and add some text. Repeat until you've got your whole process in order. That's really all there is to it. Want to add some visual interest? Insert an image via the edit menu!
Elements can be easily scaled and moved after placement, and the properties menu lets you change each item's background, border and font colors, as well as text alignment. Diagram Designer also supports multiple pages -- so you can save several charts inside one .DDD file. Your finished diagrams can be exported to several standard image formats including JPG, PNG, and GIF.
Diagram Designer is a free program for Windows and you can download it from Freeware Files. There's also an open source version that's available -- where else? -- at SourceForge.