Online software or Web 2.0 applications run on the website that you visit, there is not software to insall but you usually have to create a user account.
Free online mind mapping software, create, save and print your ideas in teh form of mind maps.
Google docs allows you to create word processed documents, presentations and spreadsheets that you can save on line adn access for any computer connected to teh internet. You can allow other people ot see or even edit teh documents and you can download them at any time to continue to edit in microsoft file formats.
Zoho is another set of online office programs that give you all the same sorts of programs and many more.