When Google Labs introduced "Tasks" to Gmail in December, we were eager for a mobile version; yesterday, the Gmail team announced an optimized Tasks web UI for mobile devices including the iPhone.
Setup is simple. First, log into your Gmail account and click "Settings." From there, click "Labs" and then the "Enable" button next to "Tasks." As Jeff Goldblum said, "There's no step three." You'll see a link to Tasks in the left sidebar of your Gmail account.
Now grab your iPhone and point Mobile Safari to http://gmail.com/tasks. Once you've logged in, you'll see the tasks you created on your Mac. Of course, you can create a task on either device, as well as multiple lists, mark items as complete and clear completed tasks. It's nice and snappy over EDGE and Wi-Fi.
Here's a great example of something that works perfectly well as a web-based app. In the rush to create iPhone/iPod touch apps that do everything under the sun, we've seen a crop of replacements for web apps that weren't 100% necessary (I still use Hahlo on occasion, if only for its speed over EDGE). If you want a free, no-frills task manager, and you already use Google for email or other services, this could be it.