Global Inbox
Gmail
Gmail rocks as web mail. Check all the lab features and its built-in search, 7G of storage. It's ideal for me.

Calendar
Google Calendar
Web based calendar from Google. Best in class, can be set to synchronize with Mail, Thunderbird, SunBird, Windows Live Mail, Outlook, Entourage... Also available on mobile phone. This is the best cross platform calendar solution I have seen so far.

To Do List
Remember the Milk
Built by an Australian company in Sydney. Provide To Do List based as web service. All web based and can be integrated into gCal. That's the best point to use it. Available on iPhone but pro account required (25 bucks a year)...
Mac OS X Dashboard Widget available: rememberthemoof

Knowledge Base Management (Wiki)
Personal Wiki based on Atlassian Confluence, it is the best enterprise Wiki. Personal license is free (2 users). In my case, Confluence 3.0.2 (upgraded from 2.10.3, 3.0.0_1, 3.0.1) is powered by Ubuntu Server, Apache, Tomcat ,Java and MySQL. 

Evernote (iPhone) and Google Docs are my temporary notes taking tools. Contents are revised and migrated to Confluence on a weekly basis.

I also have a Mediawiki instance is for legacy work related knowledge, in the middle of migrating all contents to Confluence.

Pen and Paper

Brainstorm: MindManager
Available on Mac OS X and Windows. Use Freemind on Linux. It's mind dumper, use it to dump your quick idea or thinking. Now I feel MindManager is a bit out-of-date.

File & Folder sync
Dropbox (Mac/Linux/Windows)
Inspired by Cloud computing, Dropbox offers 2GB of space for every account, client for all Linux/Mac/Windows. Easy to sync folders and files from different locations and computers.

Notes
Evernote
Best note taken service I can found at the moment. Although it is not good enough to beat Microsoft's Onenote 2007 totally, it is still the best note service. Clients available on Mac OS X, Windows. Use web based Evernote on Linux. The best part of Evernote is to use with iPhone, just take a shot and upload it, keep and back up your receipts, quick notes, post-it etc on the fly...

Address book
Google Contacts
Addressbook (Mac OS X)
Plaxo
Centralized online calendar, address book and connection solution. Plug-ins are available for Mac OS X, Thunderbird (which I think is great and most useful), Outlook/OE/Windows Live Mail, Gmail/Yahoo/Hotmail and almost all mobile devices.

Hamachi (Mac/Linux/Windows)
You have a bunch of computers at home and office or maybe somewhere else like me, right? How to easily manage and connect to each other? Try this. It's free for non-commercial.
More: LogMeIn Hamachi is a flexible VPN service that enables anyone to easily connect multiple internet-enabled computers into their own secure virtual network. This is the ultimate solution to manage multiple computers at home and office. Wonderful!

Windows Live Sync: Live Sync (Mac/Windows)
Synchronize folders automatically once set up. This is one of Microsoft's best live projects I know, the other could be Windows Live Writer. I like it. Clients available for Mac OS X and Windows. Use live ID, all folders on computers installed foldershare software will be automatically synchronized over the internet. You don't need to take care once set up. Cool!

Password Manager
KeePass (Windows) KeepassX (Mac/Linux)
We live in a world that everyone and everything asks us for a so-called password, passport. Why? I have to admit that I have a pretty bad memory and it seems that I am getting more and more forgetful. So I have to keep all my password safe. KeePass is the ultimate solution. KeePassX is the port for Linux and Mac users.

Bookmark sync: Xmarks (previously Foxmarks)
Foxmarks is a Firefox add-on, and I believe it offers support to Safari and bloody IE as well now. It's a easy tool to keep your bookmarks on Foxmarks server and keep it synchronized on all your computers. This is a MUST have add-on. Be careful to use Foxmarks with ReadItLater, do exclude the Read It Later folder in sycn profile, all your ReadItLater list will be messed up!

Read It Later (Firefox addon)
I always feel that I am overwhelmed by exploding information everyday. Too many blog entries, RSS feeds, articles to read. Sometimes I am in the middle of reading a valuable article, while I have to give up halfway because something more important comes up. Use Read It Later to mark the page, you can access your list on different machines, different operating systems. The list is synchronized using a RSS feed dedicated for you. Damn good!

Chandler (Mac OS X/Linux/Windows) Chandler's wiki is better than the product itself. It's far from a light weight GTD tool. So I ditched it.

The note-to-self organizer. A notebook you can organize, back up and share!  You must try this, wonderful concept to get yourself organized, also they offer free online backup and sheare service.

To be amended...