I just finished writing a plugin for WordPress called Wikipop. This was my first WordPress plugin, and I was pretty surprised at how straightforward the process was. If you're thinking about getting your hands dirty, check out the Plugin API page, which is really all you need to get started. Anyway, the point of the plugin is to let you link to Wikipedia articles from your posts without totally derailing your readers. Links open in an inline window like [wikipop search="Gettysburg Address"]this[/wikipop]. Click here to read more and download Wikipop.