I haven't tried uploading anything to ModDB from Dropbox, nor SkyDrive for that matter.
I just tried using an example from the public Dropbox, and admittedly I couldn't find a way to make it work.
However, I did managed to succeed with a SkyDrive link, but only after 'cheating the system', in a way.
I started downloading a file and was able to copy the direct download link (e.g:
https://orzy4a.bay.livefilestore.com/y1pvf8nlcvukWU0hzIMEHYzDUVcpKYb74T6RBqc_8wfKKWcOFM2s_sEdXvvKUxL__VgJ1UBxwDkc5AWidwduBozvg/Locators Tutorial.pdf?download&psid=1). That alone doesn't work, but once I deleted the "?download&psid=1", it DID work for each file I tried.
The same method doesn't work for Dropbox files, unfortunately. There might be a way around if you have a Dropbox account, but I'm not familiar with it.
EDIT: Bugger. Apparently SkyDrive's direct links change every day, so they're not as permanent as I thought.
I'll have a look around and see if there's a similar service which provides permanent direct links to files.
EDIT 2: Aha! Try this quick step-by-step guide:
http://www.ehow.com/how_8316162_url-file-dropbox.html
You need to have a Dropbox account and a Public folder set up, and apparently you CAN attain a PERMANENT URL which links directly to a file.
I also checked Google Drive out of interest, but like SkyDrive, its direct URLs are only temporary.
How stupid is that.
