I use Google Tasks all the time, and one of my favorite ways to use it was to have multiple lists up at the same time with a tool called gtasker. The person who created the tool seems to have forgotten about it (the domain it was hosted at, gtasker.com, has now lapsed), so I’m reposting it here:
Note that this tool may not work in Google Chrome. I have been using it in Safari without problem.
And here are a couple of other useful ways to access google tasks: