Here is a great list of what I use all the time, almost everyday
Adrive.com =50 gigs free storage Great Sub for USB sticks
Zoho.com =Everything you could ever need in an office suite online and for free (I find the notebook feature especially useful). You can log in to it with a Yahoo or Google ID or you can make your own Zoho ID.
Thinkfree.com is another free office suite online.
G.ho.st (<-----this is the actual web address...weird, I know, but type it in..it works)
=Free online "Virtual Computer" comes with 15 gigs storage and 10 gigs email storage. It has a virtual desktop, office suite, etc. It is pretty cool, and it is improving often as much of it is still in Beta or Alpha testing. They have come a long ways, however.
OfficeLive.com = Microsofts WindowsLive document storage/editing solution. I like this for storing a backup of school documents because I can upload a lot at one time and in a short amount of time. It will store powerpoints, PDFs, docs, txt, etc. files. It links with a WindowsLive Skydrive which allows you 25 gigs of free storage space (the size of what you can upload, however, is seriously limited which is why I like Adrive.com better)
http://delicious.com Is a great bookmarking site. You can export your firefox or internet explorer bookmarks and import them into delicious for easy backup. Another benifit of delicious is that it creates a by "tag" searchable database of your bookmarks.
http://www.go2web20.net/ Is a great site to look for things that will do whatever you need online instead of based in hardware land. Office suites, virutal desktops, notebooks, storage, file hosting, etc. etc.
http://bubbl.us/ Awesome brainstorming tool I've used with classes and with individual kids who needed visual mindmads for organization. What you create, you can save and export, print, etc.
http://280slides.com/ is a spiffy presentation editor. If kids work on stuff at home, it is an option if they do not have access to a software based office suite.
Art/Online color illustraters for us Non-smart board people.
Online Chart Maker- iChart
An online PDF annotater/editor
I also use google's host of products-Docs office suite and storage, reader, email, youtube, picassa web albums etc. You can find a list of everything google has to offer here:
For secure password storage, I use https://lastpass.com/ which is absolutely awesome. It remembers passwords and site logins for all the awesome resources I use on a daily basis;)
I use this extension sometimes to clean up a printable worksheet or a reading that is cluttered with too many ads or perhaps slightly more mature themes than I want in some places depending on the age group of the students.