Saving an iMovie videos to your Dropbox account is easy. When you create a video on an iPad, there are many ways to share it with others. You can also share your video to online publishing sites like Vimeo, Youtube and much more. If you want to upload videos to Dropbox from iMovie, then first download that video to camera roll on your iPad. Dropbox has a feature 'Camera Upload' that allows Dropbox to sweep the Photo Roll of an iPad. You can share Dropbox photos and videos via a link in an email.
You can install PicBackMan's Dropbox uploader for Mac from the website and start backing up photos and videos.
Quick Tip to ensure your videos never go missing
Videos are precious memories and all of us never want to ever lose them to hard disk crashes or missing drives. PicBackMan is the easiest and simplest way to keep your videos safely backed up in one or more online accounts. Simply download PicBackMan (it's free!), register your account, connect to your online store and tell PicBackMan where your videos are - PicBackMan does the rest, automatically. It bulk uploads all videos and keeps looking for new ones and uploads those too. You don't have to ever touch it.