Do you want to preserve your blog or anothers blog for ever? Well obviously get it web archived. However if you are of a mind to create something book like you now can do that too.
There have been a number of successful blogs, that have transitioned into books (Stuff White People Like being a prime example). This blog is not one of those.
But here anyway is a new tool.
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.
But oh, it doesn’t work with WordPress.com blogs, so again no book-making from here.
But wait, there are a number of other commercial and non-commercial options for exporting WordPress.com and Blogger (blogspot) blogs into a book-like form. See Blurb for an example.