Dropbox: I love this. There are others like it but I believe this one to be the best. Instead of emailing your documents to yourself or putting them on a flash drive in order to view them on another PC, just save them to your "Dropbox" folder on you PC. Once you do that an exact copy is uploaded to your online Dropbox folder so that you can access it anywhere, anytime.
Let's say you made a simple To Do list using Notepad on your office PC. You save it to your 'My Dropbox' folder (located in your Documents folder by default). You go home and remember a couple of things to add to your To Do list. Since you also have Dropbox installed on your home PC, the new To Do list will already be there in the 'My Dropbox' folder...no need to open up the online folder. Whatever changes you make to that list will show up on your office PC the next time you view it.
There is also a free Dropbox app for iPhone/iTunes/Blackberry and such. So I can view any document, file, pic or whatever is on My Dropbox on my iPhone. The free version gives you just 2GB of space but so far that's all I need. I learned about this from a guy who is writing a book. He writes using a word processor and saves all pages to his Dropbox instead of his desktop or some other folder on his laptop. That way if it gets stolen, he doesn't lose his work in progress.
There is also a 'Public' folder within Dropbox. Whatever you put in there can be viewed by people of your choice by generating a view link that can be sent to them.