Here are some Free alternatives to comic sans.
Comic Sans is ugly. Just don't use it. It may have served a purpose in it's time but now you can easily find far better fonts suitable for Mac OS X, Windows and Linux.
This list is more of a list of fonts which could replace Comic Sans in various situations. A good example is that people often use Comic Sans as a kids font (urrg poor kids). These font's don't necessarily LOOK like Comic Sans but hopefully you'll find something nicer from this list.
One last thing, my personal favourite Comic Sans replacement is a font called Noteworthy which is used by the Apple notes app and installed by default on a Mac. If you have a Mac look it up, if not I apologise but I can't put it in the list because I can't find it for free (there is a free font called noteworthy, but it's a different font entirely - a really ugly one).
Here they are, Comic Sans alternatives/replacements:
Zag Font (2 Styles free)