- Kindle 1: http://s3.amazonaws.com/G7G_FirmwareUpdates_WebDownloads/Update_kindle_1.2.bin
- Kindle 2: http://www.amazon.com/update_kindle2.bin
- Kindle DX: http://www.amazon.com/update_kindle_dx.bin
Amazon replaced the previously useful Kindle Software Update page with an announcement for the 2.5 firmware which will be released in the future. In the process, they removed the download links for manual firmware upgrades.
I'm mostly putting up these links for my own reference, but maybe they will help others as well.