See the column for a description of the value of Dropbox. Links mentioned in the column are here.
Dropbox is so widely used, many have built little utilities to make it even more useful.
I mention in the column one of its best uses is to unify the eco system between your PCs and your phone. I can save a file to Dropbox on my PC, and view it on my phone.
Note: I have't used most of these tools except where noted.
What if you get an email on your phone with an attachment you want to store in your Dropbox? iOS on Apple products (iPad, iPhone etc.) won't let a user save a file to Dropbox. My GMail app on my Android phone won't let me either. Enter sendtodropbox.com. This free service links to your Dropbox and gives you an email address. Any email you send to that address with an attachment, automatically puts the attachment into your Dropbox. This service, I have used.
To make it easy for people to upload a file to your Dropbox, you can embed a form from JotForm that does the trick.
Another one I have yet to try is DropPages. It lets you host a simple website with Dropbox.
There are Dropbox apps for both iOS and Android.
If you are an iPad user, Apple's own Pages and Numbers word processing and spreadsheet apps do not save to Dropbox. This website shows a way to make them do it.
There are apps that will let your directly edit files on Dropbox on your iPad, like PlainText. PlainText is free and works with simple text files. Apps like Documents to Go and QuickOffice let you edit Office documents in Dropbox. There are other apps in the Apple App Store. Just search for Dropbox to find them.
GoodReader and iAnnotate let you read PDF files from Dropbox and even annotate them.
On Android, there is QuickOffice and Documents to Go as well. I use MyNotes to edit text files from Dropbox on my Android phone.
You can see all the Android apps that mention Dropbox with this link.
People are always coming up with new and interesting uses for Dropbox. This blog post lists many good ideas.
If you don't have a Dropbpx account and want a free 2 gigabyte account, you can click here to join Dropbox with an extra 256 megabytes (and give me 256 megabytes extra for referring you).