If you want others to be able to send you large files, that are too big to email, for example, you could use a shared folder. However, if you just want a single file without the hassle of a shared folder, web service DROPitTo.me will get it done.
Sign up for free, and you’ll get an upload link that you can send anyone to upload a file to your Dropbox. You can make it password protected so that only those you want to access it can. The service is simple and fast, and well worth a look.