Greg did this over a year ago, but I just stumbled on it now. Pretty neat:
You can specify in the URL how many entries to return, and which logs to use. For example, http://example.org/Rss.aspx?num=20&logs=Application,System would return the 20 most recent entries, looking in both the Application and System event logs.
Download here - requires ASP.NET. If your server is on the internet rather than local, try it with my HTTP security samples to securely monitor the event log of the remote server - very handy for those hosting on remote, dedicated servers.