Windows/Mac/Linux (Adobe AIR): We've written about a lot of desktop clients that are essentially site-specific browsers (SSBs), but free AIR client Google Tasks helps you consolidate your clients by allowing access to most Google apps in mobile form.
Google Tasks may be one of the lesser-used Google services, but for those who like their task integrated with everything else Google in their lives, it certainly does the trick. Now, thanks to the same developer as Remember the Task (a desktop client for Lifehacker-favourite Remember the Milk), you can get Google Tasks in a small window on your desktop — plus so much more.
The really cool thing about the Google Tasks client is that, since it's merely built on the Google Mobile API, you can actually access any Google app available as a mobile site from Google Tasks. Just scroll to the top and choose your app (or hit "more" for a larger list), and you can access Gmail, Google Calendar, Google Docs, and others within the same client, essentially making it an all-around Google Mobile client. If you feel like you have one too many SSBs open at any given time, this is a pretty nice solution.
Google Tasks is a free download for all platforms, and requires Adobe AIR.