I've previously downloaded some of the available DNN Google Sitemap Generators, and they work well - until you have a more complicated module like the Blogs module. The Blogs module uses the same page but has it's own redirects to show all the blog / blog entries on the one tab. As such, a standard Google sitemap generator isn't going to show all the relevant URL's properly.
What I've developed is an extensible DNN Sitemap generator using the ASP.NET Provider model. It consists of a HTTPHandler to receive the request for a Google sitemap, and a default DNN Sitemap provider. The Provider model allows the development of module - specific Providers as well.
The way it works is that the default Google Sitemap Provider checks for module-specific providers based on the ModuleDef friendly name and the name of the PRovider in the web.config. When it finds a match, it calls the module-specific provider to get the list of URL's for that particular page/module combination. This is all configured through the web.config, so a site made up of many different custom modules can have a provider dropped into the \bin directory for each specific module without having to recompile anything.
On my blog entry about this topic, I have provided free source and demo projects for download. This includes the 'standard' DNN Google Sitemap generator, and an implementation of a module specific provider for the Blogs module. This shows how to develop a custom-module specific provider from the base default provider plus gives a free blogs-specific Google sitemap provider.
See my Blog Entry on the DotNetNuke Google Sitemap Generator here
To look at the source code, you'll first need to download the demo project and set up the references to the DotNetNuke modules, as well as the iFinity.Utilities module.
The Generator is built with C# in NET 2.0 and is designed for DotNetNuke version 4.02 and upwards. Sorry, I don't have a NET 1.1 or DotNetNuke 3.x version.
I'm happy to give this work over to the DotNetNuke community as the original idea came from other free downloads. Feel free to post back to this thread for asking questions about it. If you're unhappy with it, I'm still refining the model and appreciate feedback. If you're happy with it, feel free to implement it into your site, and I appreciate links back to the blog entry so I can get the word out.