There's a new hot ebook making tool this week called Anthologize. It's a WordPress 3.0 plugin that you can use to convert blog posts into ebooks. From the About page:
Anthologize is a free, open-source, plugin that transforms WordPress 3.0 into a platform for publishing electronic texts. Grab posts from your WordPress blog, import feeds from external sites, or create new content directly within Anthologize. Then outline, order, and edit your work, crafting it into a single volume for export in several formats, including—in this release—PDF, ePUB, TEI.
Please note that Anthologize cannot be installed on blogs hosted at WordPress.com.
It requires 3.0, so I can't use it until I upgrade. But it's on my todo list.