Postica's a latecomer to the free online sticky notes arena, but it carries with it a few neat features that set it apart. First and foremost is the ability to attach any kind of file (up to 5 MB) to a sticky note, and then send that note to a friend, whether or not they have an account. Secondly, Twitter users can share notes and create new notes on their board, even designating the colour, by direct-message
postica. For organising a multi-file project by yourself or in a group, Postica's a simple but attractive option. Postica is free to use, requires a sign-up.