While Dropbox public links are very useful for sharing files with your friends, a lot of files (text files, MP3s, PDFs and others) will automatically open up in their browser. Here's how to get them to download to their hard drive instead.
Lifehacker reader the-soup explains a simple URL trick to tell Dropbox to download a file:
If you want a Dropbox public link to download instead of show in your browser, add ?dl=1 to the end of the link. This only works for files in your public folder, with the links like http://dl.dropbox.com/u/*******/ketchup.png and not for the ones that are like https://www.dropbox.com/s/****************/Natan.ttf.
It's a simple tip, but it's actually pretty useful if you're trying to share files with your less tech-savvy friends. I know if I shared, say, an MP3 file to them via Dropbox, they wouldn't know how to save it to their computer from their browser's built-in music player. By adding this link, you save yourself the trouble of explaining how to get that file into, say, iTunes from that browser window.