I'm not sure if this has already been posted, but I did a quick search and didn't find it here so figured I would post it. I usually post on card trading sites and the ones that have this feature sure do save a lot of scrolling it seems. That and you can post some fun "suspense filled" maildays.
I inserted the following code into the bbcode.cs file after the declarations already there.
Code:static private Regex r_spoiler = new Regex(@"\[spoiler\](?<inner>(.*?))\[/spoiler\]", m_options);
And then this in the makeHTML function.
Code:
// spoiler
NestedEmbedReplace(ref bbcode, r_spoiler, "<div style=\"margin:0px; margin-top:0px\"><div class=\"quotetitle\"><input type=\"button\" value=\"Spoiler\" style=\"width:55px;font-size:12px;margin:0px;padding:4px;background-color:#C0C0C0;\" onclick=\"if (this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display != '') { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = ''; this.innerText = ''; this.value = 'Hide'; } else { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = 'none'; this.innerText = ''; this.value = 'Spoiler'; }\" /></div><div class=\"quotecontent\"><div style=\"display: none;\">${inner}</div></div></div>");
The usage is pretty standard.
Code:[spoiler]stuff you want to hide.[/spoiler]
Anyways, hopefully this will be useful to someone else. At the very least it will help me not have to look for the code again when I inevitably lose track of my mods!

-R.