For those too lazy to click the link @
AgentTadpole provided:
[B] for bold
[I] for italic
[U] for underline
[S] for strikethrough
[COLOR=color] for color
[FONT=fontname] for font
[size=size] for size
[url] for links
[email] for email links
[url=link] for hyperlinks
[email=address] for email hyperlinks
[user=id] for linking to user profiles. "@ Username" can also be used, and will notify them; forget the space.
[img] for images
[media=site] for embedded media
[list] for lists (use [*] for bullets, and [list=1] for numbered lists
[left] left-alignment
[center] for center-alignment
[right] for right-alignment
[quote] for quoting
[code] for general code
[php] for php code, highlighting syntax
[html] for html code, highlighting syntax
[indent] for text indentation
[plain] to avoid bbcode
[attach] for attachment insertion
[float=option] use of a floating div
[h2] adds a level 2 header
[spoiler] for spoilers
[user] for usernames