If you have Bravenet's Pro Email Forms service, you can add a field of type="file" and name="userfile". This will create the necessary "browse" button so the user can select a local file to send you. The file size limitation is 2MB and more detail can be had in the Bravenet Email Forms FAQ and Tutorial.
There are also some free email forms services that offer file attachments. For example, Mail-Maniac.com is a free service that allows file attachments up to 320KB. This is usually sufficient for most purposes.
A google search may bring up other methods that allow users to get files to you.