What I enjoy most about open source is when people take existing products and twist them around into new shapes. I've long had high regards for PortableApps for doing that, but thanks to a commenter on a previous post of mine, I now have a new crew to watch in that regard: BitNami.
BitNami is a series of repackagings of common server-side open source applications, deployed in simple packages that take mere minutes to set up and get going. Think of it as PortableApps for a server: WordPress, MediaWiki, phpBB, Drupal, Joomla, and many more server-side apps are available as BitNami packages, with more on the way (like SugarCRM). All BitNami packages include the app itself, a Web server, and whatever database solution you might need.
Since many of the common applications you need have certain dependencies that have to be satisfied (PHP, Perl, Apache, MySQL, etc.), a BitNami "stack" is best if you don't already have the other components needed for a given application. For instance, if you want to give WordPress a trial whirl on your local Windows or Linux machine, you can snag the BitNami version, unpack it locally, and run it there. If you like the results, you could then export the database from WordPress to a flat file, reimport it on a server where WordPress already is set up, and pick up where you left off.
If you'd rather just get an infrastructure stack -- Apache, MySQL, and PHP -- and manually deploy server applications on top of that, BitNami has AMP stacks for Windows, Linux, Macintosh, and Solaris all ready to go. The Windows AMP stack is vaguely similar to the XAMPP stack that's also available in a PortableApps implementation, although XAMPP appears to have a lot more in the box than BitNami's stack. You go with what you need.
My plans for BitNami include a local tryout of MediaWiki and maybe Mantis, and I've voted for them to package Asterisk, Plone, and Open-Xchange Server in the next round of additions. I'd like to see them add Movable Type, personally, but if you have a preference of your own that's not in the polls yet, head over to the forums and make a suggestion.