Even if you have a great memory, you won't be able to remember everything. And there is so much to remember all the time: websites, tasks to do, work, meetings, new ideas or random thoughts. There are many handy websites and applications to store your notes online. Most of them also work with your phone, e-mail, Twitter etc.
Although I think it cannot replace the occasional scribbles & doodles in your notebook, it's a great way to save paper.
Evernote (my favorite)
Evernote makes it easy to remember things big and small from your notable life using your computer, phone, and the web: type a text note. Clip a web page. Snap a photo. Grab a screenshot. Everything you capture is automatically processed, indexed, and made searchable. You can add tags or organize notes into different notebooks. Search for notes by keywords, titles, and tags. Evernote makes printed and handwritten text inside your images searchable, too.
Worth reading: 100 Different Evernote Uses - Andrew Maxwell
In brief, NotePub provides real time sharing and searching of notes with read/write permissions set for each note and user. NotePub is very straightforward, yet it lets you do most things you could with previous software concepts such as blogs, wikis, forums, email, chat, and social networks.
UberNote is a knowledge management tool enabling you to quickly store and access your content from anywhere. Easily submit notes using email, IM, and mobile devices or clip web content with the browser toolbar. With UberNote you can instantly access your notes and benefit from your own knowledge. You can store anything you want, like task lists, contacts, bookmarks, web clips, passwords, documents and text files in your "My Documents", notes to self, meeting notes, recipes, research or any random thoughts or ideas.
MyNoteit - An online note taking tool for students
- Take, edit and share notes online.
- Easily search and share notes.
- Manage tasks with your to-do list.
- Don't forget anything with your calendar.
- Stay in the loop with class groups.
MyStickies, Sticky Notes for the Web
MyStickies lets you save the web for later: To put it simply, MyStickies allows you to place little yellow squares of digital paper anywhere and everywhere you feel like in the whole wide web. Along with the ability to put sticky notes on webpages mystickies offers a powerful interface to browse, search, sort, edit and generally have a wonderfull time with your sticky notes from any computer that has internet access.
There's more of course: also check out "Top 10 Online Note Taking Applications" on Mashable.