Quickly add a trailing slash in the URLs if it's missing in the permalink structure.
When your permalink structure does not end by a trailing slash (/), all your links look like http://example.com/2009/05. Permalink Trailing Slash Fixer add the missing trailing slash.
If you have a site with the following permalink structure
/%category%/%postname%.html and your permalinks
look like these:
After activation of the plugin: