The servicemark (SM) is quite the unusual little character on the web. One might assume that it would act like the copyright symbol (©) or the trademark symbol (™) and have its own special HTML entity code, but alas, this is not the case.
The obvious solution is to use the <sup> tag, but… it doesn’t look that awesome.

It’s not the end of the world, but it’s a bit large for our purposes and doesn’t really look like a trademark-type character, just some floaty text.
There is a unicode character that represents this mark, which can be displayed as
but unfortunately it really isn’t that well supported. Many fonts don’t have this character defined, and even if they do, it usually doesn’t show in IE and instead renders as an empty box. Frustrating!
Fortunately, there is a way around this, as discovered by someone named Tim McCormack:
Lucida Sans Unicode is one of the few fonts that does support the servicemark character. Therefore, if you put a span around your unicode character and set the styles for that span to render it in Lucida Sans Unicode, it appears to work in most browsers.
HTML:

CSS:

And the end result:

The text is now smaller, still superscript, and more trademark-esque. Bonus: It works in IE6!