8
In the template for system_block_mainmenu.html after the line:
<!-- end module menu loop -->
Add the following..
<!-- Add a static menu entry -->
<a class="menuMain" href="{LINK}">{DESCRIPTION}</a>
Wash, Rinse, Repeat...
If you are linking to something, under XOOPS you can do something like the following..
<{$xoops_url}>/modules/cjaycontent/index.php?id=2
The only downside of this is that it doesn't "mix" w/ your other entries in the menu...