PA just came out with a version:
http://portableapps.com/apps/office/kchmviewer-portable
Synopsis: Tool for looking at CHM-format ebooks, frequently used for help files (CHM means "Compressed Help Manual) Very happy to see this. Windows can already view CHM files but this looks familiar (but improved) and has more features than the default viewer: zoom, bookmarks, even extracts CHM content so you can send someone (for example) just a page or two from a HOWTO to solve a problem.
Additionally, when I create help files, it's important to make sure non-Windows computers can view them. It goes a long way to creating a standard for self-contained help files.
Cross-platform (Linux/Win)
Anyway, very happy the folks at PA took the initiative to make this available.
Wishlist:
* support drag and drop
* Ability to open multiple CHM files at once (I think this is on the way ... the menu system seems to be prepared for this)
* Support for other ebook formats
License: GPL v3
Bumping this thread over to submission...