standard tags:

standard tags are available to everyone wihtout any restriction

bold: [B]text[/B] makes bold text
italic: [I]text[/I] makes italic text
underlined: [U]text[/U] makes underlined text
strike through: [S]text[/S] makes strikethrough text
subscript: [SUB]text[/SUB] makes subscript text
superscript: [SUP]text[/SUP] makes superscript text
color: [COLOR=red]text[/COLOR] or [COLOR=#FFAA44]text[/COLOR] makes text color red or #FFAA44
size: [SIZE=80]text[/SIZE] makes text 80% of normal size
font: [FONT="Lucida Console"]text[/FONT] sets the font to courier
align left: [LEFT]text[/LEFT] aligns text to the left
align center: [CENTER]text[/CENTER] aligns text to the center
align right: [RIGHT]text[/RIGHT] aligns text to the right
code: [CODE]text[/CODE] to write code
quote: [QUOTE]text[/QUOTE] to write quoted text
link: [URL=http://mylink.com/]text[/URL] or [URL]http://mylink.com/[/URL] makes a link
image: [IMG]http://image_link.com/[/IMG] or [IMG WIDTH=200 HEIGHT=50]http://image_link.com/[/IMG] or [IMG HEIGHT=50]http://image_link.com/[/IMG] makes an image
list:
[LIST]
[*]apple
[*]banana
[*]piment
[/LIST]
makes an unordered list, and
[LIST=1]
[*]apple
[*]banana
[*]piment
[/LIST]
makes an ordered list
smileys: [smiley]:)[/smiley] or [smiley]:P[/smiley] makes smileys
tables:
[table width=100% bg=#CCCCCC]
[tr][td] row 1 column 1 [/td][td] row 1 column 2 [/td][/tr]
[tr][td width=15px bg=blue valign=top colspan=2] row 2[/td][/tr]
[/table]
makes a table

3rd party tags:

3rd party tags can be more or less restricted depending on the config of the admins. they are a safe way to allow people to add cool stuff to their posts.

facebook like button: [LIKE] embeds facebook like button in the post
twitter tweet button: [TWEET] embeds twitter tweet button in the post
google +1 button: [+1] embeds google +1 button in the post
addthis button: [ADDTHIS] embeds addthis button in the post
youtube video: [YOUTUBE WIDTH=100 HEIGHT=100]http://www.youtube.com/watch?v=xxxXXxxXx[/YOUTUBE] embeds a youtube video in the post
novamov video: [NOVAMOV]http://www.novamov.com/video/xxxxxxxxxxxxx[/NOVAMOV] embeds a novamov video in the post
stagevu video: [STAGEVU]http://stagevu.com/video/xxxxxxxxxxxxxxx[/STAGEVU] embeds a stagevu video in the post
tudou video: [TUDOU WIDTH=100 HEIGHT=100]http://www.tudou.com/programs/view/xxxxxxxxxxxxxxx/[/TUDOU] embeds a tudou video in the post
youku video: [YOUKU WIDTH=100 HEIGHT=100]http://v.youku.com/v_show/id_xxxxxxxxxxxx.html[/YOUKU] embeds a youku video in the post
56.com video:
[56.COM WIDTH=100 HEIGHT=100]
<embed src="http://www.56.com/n_v198_/c49_/14_/17_/ccf_win_/xxxxxxxxxxxxxxxhd_/xxxxxx_/0_/xxxxxxxx.swf" type="application/x-shockwave-flash" width="480" height="395"></embed>
[/56.COM] embeds a 56.com video in the post
google maps:
[GOOGLE_MAPS]
<iframe width="425" height="350" frameborder="0" scrolling="no" marginheight="0" marginwidth="0" src="http://maps.google.com/?ie=UTF8&amp;ll=46.225453,-64.962158&amp;spn=3.739548,7.064209&amp;t=h&amp;z=7&amp;output=embed"></iframe><br /><small><a rel="nofollow" href="http://maps.google.com/?ie=UTF8&amp;ll=46.225453,-64.962158&amp;spn=3.739548,7.064209&amp;t=h&amp;z=7&amp;source=embed" style="color: #0000FF; text-align: left">View Larger Map</a></small>
[/GOOGLE_MAPS] embeds a google map in the post
veoh video: [VEOH WIDTH=100 HEIGHT=100]http://www.veoh.com/browse/videos/category/anime/watch/vxxxxxxxxxxxxxx[/VEOH] or [VEOH]http://www.veoh.com/browse/videos#watch%3Dvxxxxxxxxxxxxxxxxxxx[/VEOH] embeds a veoh video in the post
hulu video: [HULU]<object width="512" height="288"><param name="movie" value="http://www.hulu.com/embed/xxxxxxxxxxxxxxxxxx"></param><param name="allowFullScreen" value="true"></param><embed src="http://www.hulu.com/embed/xxxxxxxxxxxxxxx" type="application/x-shockwave-flash" width="512" height="288" allowFullScreen="true"></embed></object>[/HULU] embeds a hulu video in the post
myspace video: [MYSPACE_VIDEO WIDTH=100 HEIGHT=100]http://vids.myspace.com/index.cfm?fuseaction=vids.individual&videoid=xxxxxxxxxxx[/MYSPACE_VIDEO] embeds a myspace video in the post
barbavid video: [BARBAVID WIDTH=400 HEIGHT=200]http://barbavid.com/video/xxxxxxxxxxxx[/BARBAVID] embeds a barbavid video in the post
vidxden video: [VIDXDEN]http://www.vidxden.com/xxxxxxxxxxxx/pawn.stars.s01e01.dvdrip.xvid-wide.avi.html[/VIDXDEN] embeds a vidxden video in the post
vidbux video: [VIDBUX]http://www.vidbux.com/xxxxxxxxxxxxxx/xxxxxxxxxxxxxxxxxxxx.html[/VIDBUX] embeds a vidxden video in the post
gorillavid video: [GORILLAVID]http://gorillavid.com/xxxxxxxxxxxxx[/GORILLAVID] embeds a gorillavid video in the post
putlocker video: [PUTLOCKER]http://www.putlocker.com/file/xxxxxxxxxxxxxxx[/PUTLOCKER] embeds a putlocker video in the post
sockshare video: [SOCKSHARE]http://www.sockshare.com/file/xxxxxxxxxxxxxxx[/SOCKSHARE] embeds a sockshare video in the post
videoweed video: [VIDEOWEED]http://www.videoweed.es/file/xxxxxxxxxxxxxxxxx[/VIDEOWEED] embeds a videoweed video in the post
divxstage video: [DIVXSTAGE]http://www.divxstage.eu/video/xxxxxxxxxxxxx[/DIVXSTAGE] embeds a divxstage video in the post
movshare video: [MOVSHARE]http://www.movshare.net/video/xxxxxxxxxxxxxxxxxxxx[/MOVSHARE] embeds a movshare video in the post

risky tags:

risky tags are only available to those who have the power of using them.

flash: [FLASH]http://website.com/flash_movie_url.swf[/FLASH] or [FLASH width=200 height=50 flashvars=&var1=test&var2=test]http://website.com/flash_movie_url.swf[/FLASH] embeds flash in the post if you have the power to do it on this forum, otherwise it will only show a link to the flash movie
iframe: [IFRAME]http://website.com/frame[/IFRAME] or [IFRAME width=200 height=50]http://website.com/frame[/IFRAME] embeds an iframe in the post if you have the power to do it on this forum, otherwise it will only show a link to the framed page
html:
[HTML]
<p>this is a paragraph</p>
[/HTML]