One of the problems of the current generation of app stores is apps can sneak in, and you don't even know about it. I realized today that Dropbox has created finally their own Windows Phone client that seems to work pretty well. You can find the details here
There is also a Windows Store app here but I typically just like the way the sync client works and it just is "there" on your local drive and not have to worry about using an App.
Few days ago apparently they also released more integration with Office Online read the blog post here. It let's you open Dropbox files for use inside the web app versions of Word, etc. It's actually pretty easy to try - if you are logged into your Dropbox on your web Browser - go to Word in Office.com and you should see the following dialog prompting you if you want to Add Dropbox support.
And if you don't right away and want to come back later to connect Dropbox - you can do it from the lower left corner where you will see the "Add a Place" link. When you click on that, you will see the following.
I was able to do this with both the home version of Office and the business version of Office.
Speaking of the home version of Office.com, if you haven't seen the work and play deal Microsoft is running if you use any of the services - details here. You get Office Home + Skype World Unlimited Calling + XBox Live + XBox Music Pass for $149 for a year. I was paying that much for Skype and XBox Music, so basically got the others for free.