Windows and Mac: Insync is a service that syncs Google Docs with your local machine so you don't have to use your browser if you'd prefer working in another word processing app.
If Insync sounds familiar, we offered you beta invites a little over a year ago. Now the service has launched and has focused itself on Google Docs. This doesn't mean you can only sync documents. I had no trouble adding a ZIP file to my account, and it showed up in the Insync web app as well as Google Docs.
What's also really useful about Insync is that you can manage multiple Google accounts. If you're used to dealing with more than one account, you know this can be kind of a pain even with multiple sign-in enabled, so being able to combine them into one location can be very useful.
All your storage costs are through Google, so you get 1GB for free and additional space is very cheap. Currently Google charges $US5/year for 20GB, $US20/year for 80GB, $US50/year for 200GB, and so on (up to 1TB). To compare, Dropbox charges $US50/year for 50GB and $US100/year for 100GB. Since Insync allows you to essentially sync whatever you want to your Google Docs account, it's quite a bit cheaper space-wise. Insync also offers very finely-tuned sharing permissions, letting you decide the level of control someone has over a file you share with them — even whether or not they cant share re-share that file with someone else.
Depending on your usage, Insync could very well be a cheaper replacement for Dropbox. As far as I can tell you can sync whatever you want with it. My Dropbox account is stuffed with over 80GB of files at the moment, so I haven't tested how Insync would handle that large amount of data, but it handled whatever files I threw at it without issue. If you've been looking for a good Dropbox alternative, you'll want to take a look at Insync.