These are some of my favorite productivity tools:

Firefox- Browser
Adblock Plus- Add-on for Firefox. Never/Rarely see an ad again! Seriously. Here's an example:

Google Docs:

Google Calendar- Easy way to share calendars

Google Reader

Tiny URL- Shorten web addresses

PDF Creator- (download) "Print" to PDF format

Jing- (download) Capture images, record video of onscreen action

Dropbox- online file storage