The boards use html, with a few additions of [tags] listed in the "Smiley Codes" that is linked to on the left side menu thing to emulate some bbcode.
Unfortunately, links are too complicated to be done using the simple find/replace mechanism that the smiley codes use.
To create a link in html, you can use
<a href="http://www.yourlinkhere.com"
>text to display
</a
><a href="http://www.maxminis.com"
>Visit the Maxminis Forums!
</a
> =
Visit the Maxminis Forums!<a href="http://www.wizards.com/default.asp?x=dnd/minis"
>http://www.wizards.com/default.asp?x=dnd/minis
</a
> =
http://www.wizards.com/default.asp?x=dnd/minis