Astrid is Google's official personal task manager for Android, and it shows. This app won me over with its rich features and navigable design a few weeks ago. It is the highest rated in the Market of all such apps, with 4.5 stars.
TooDo is a powerful organizer that has read/write synchronization with Remember the Milk and ToodleDo. My primary complaint with the program the last time I looked at it was unnecessary weight - I only wanted the RTM functionality. While there isn't an RTM-only functionality, significant changes have been made. The app now has a "lite mode" - where categories and context are disabled. It makes for a simple, light checklist. However, the "non-light" mode has become even more robust. With notification bar and color-coded LED integration, TooDo is looking better than ever. There's a bit of a learning curve, but if you are looking for an all-in-one solution, this is one is worth some of your time. TooDo has 3 stars in the market.
Tasks, by VNSN has 3 stars in the Market. The app's description points out its small size as a selling point (Tasks is free). It uses a two-level hierarchical system: lists and notes. You create a list, say "Homework," and you put notes within that list. It is simple, solid, and conforms to the user; rather than the other way around. I like this program.
Tag ToDo List by Teo stands out in the market. Not only can you tag your tasks as the name implies, you can record voice notes to your SD Card, draw graphical notes, and look at statistics. This is also a good one for people who love keyboard shortcuts. It comes with a task list for learning how to use the app, and has a polished, clean interface. Tag ToDo has 3 stars in the Market, but probably deserves more.
RTM ToDo Viewer has 2.5 stars in the Market, which would normally cause me to pass it by. But I am a supporter of Remember the Milk on all platforms and am happy to see someone is working on a dedicated Android client. It is currently read-only. The programmer, Marcel, started it for fun and learning. He did say he hopes to implement write functionality in the future. That would increase the ratings, for sure. RTM clients are available for your computer, and having them all sync up is great.
Doogle is another exception to my 3-stars-and-above-only rule, with 2.5. Here's why. Tasks include contact integration and hardware functions, like making a call at a certain time. It needs some time to mature, but I like the idea. I'll be looking for updates. Maybe we'll take a look back at this one later.
ToDo List Free is a demo with shoddy graphics and 3 stars. I wouldn't recommend this program. It is the only one on this list (that I know of) with a price. It is also the least deserving of your cash. Sorry, creators. I'm not sure what you're up to here.