Attempting to create a tag cloud, or something similar.

Specifically, I'm cataloging a sizable collection of books and I'd like to be able to attach descriptors to them, such as 'Humor' or 'Astronomy', by which the collection could then be filtered.

Unfortunately, Autofilter isn't very smart and I can't seem to get it to recognize multiple items in one of the cells under 'Descriptors' as being multiple items; instead, it parses, say 'Biology, History' as being a third category distinct from either History or Biology. Which makes attaching a variable number of descriptors to different books something of a pain.

Is there some way I can go about this, either by entering multiple distinct items into a single cell or by getting fancier? I'm currently using Excel 2003, but I can upgrade if necessary.

EDIT: This was originally to be titled 'A tag cloud', hence 'a tags.' It doesn't seem that I can edit the title of the thread, so I'll just have to live down the typo.