The newest build is 0.2.1. (It will be available at midnight tonight!)
Download Chimera here. The MIME type from the Netscape server is incorrect, so instead of clicking on the link, use your context menu to "Save Link As...".
What's New In 0.2.1
Find in Page and Find Again are now implemented.
Chimera will now remember your window's size and position across launches, so you don't have to constantly resize your browser window any more.
Chimera will now move and shrink a browser window as necessary to accommodate the sidebar. If you don't move the window, then it will also return to its original size and position after you close the sidebar.
Context menus are now in place for all objects (links, images, input fields). Several commands have been hooked up, including Back/Forward/Reload, the ability to open links in new windows and tabs, and the ability to save links and images to disk (although you won't see any progress yet while saving).
Chimera has fully implemented popup blocking, in a way that is actually accessible to novice users. Chimera can detect whether a popup is of the evil variety and offers to enable popup blocking when it encounters one of these popups. Click Ok and you'll never be bothered by popups again. No mucking through advanced or obscure preferences to figure out how to block popups. Chimera takes care of this for you.
The bookmarks sidebar has been revamped with all new icons. Menu bookmarks will now show up after you add them. The sidebar has a new bookmark task bar for common actions such as creating a bookmark, editing a bookmark, creating a folder or removing a bookmark.
You can now use Option+Click to save links (although again, no progress indication will be given yet).
Other miscellaneous fixes: The horizontal scrollbar problem has been fixed in 0.2.1. Tab keyboard navigation has been improved. Textfields no longer have trouble accepting input. The Home gaffe (mapping to the cycle windows key) has been fixed. The sidebar crashes have been fixed.
Chimera has complete build instructions on mozilla's Web pages (under the code name ChimChim). You can find those instructions here. Be aware that the downloadable build listed above contains numerous patches to Mozilla that have not yet been accepted, so any builds that you do will not be as stable or as performant as the downloadable build above.
If you have questions about building, use the chimera mailing list or hop on to #mozilla, and someone can help you out.