Amazon has just released a software update for 2nd generation and DX Kindles. First-gen owners are out of luck.
The 2.3 version update goodies for U.S. and international wireless eReaders include an 85% increase in battery life (that's about up to two weeks from just one), manual screen rotation from portrait to landscape, the availability to convert PDF files to the Kindle format, and a built-in PDF reader.
For DX models, specifically, will also get the option to convert PDF files to Kindle files and an extended wait time before the screensaver kicks in (from 5 up to 20 minutes now).
If you are a proud owner, you can download and install the update via USB. For the upgrade files and more detailed instructions, visit Amazon's specific FAQ page on version 2.3.