As GOOGLE is still not providing a ToDo app (a lot of rumor about it, but no solution yet) i looked for online ToDo / GTD applications and tried RememberTheMilk, TaDaLists and Todoist. While RememberTheMilk seems to be most hyped i prefere Todoist after a short periode of usage. Simple, straight but powerfull.
I completely miss Palm Treo sync, but that's another story.
If you have additional suggestions i'd love to hear.