There’s an easy way to having your posts end in a .html extension, using the permalinks option within WordPress.
Following the example used on properly terminating permalinks, you could have a page like http://www.crazylinks4free.com/2008/12/great-free-directory.html with this rule:
/%year%/%monthnum%/%day%/%postname%.html
Note that this does not generate static .html files. It only adds the .html extension, pages are still being dynamically generated.
This is reported to improve the blogs search engine optimisation, but also can be useful if you want to migrate to a different blog engine (away from WordPress), since the pages can easily be made static and retain their URL structure.
Related posts: