Some neat (and useful) work from a talented team at UTEP and SDSC: an integration of the GridFTP protocol into the Firefox browser (to be released in final form later this year, I believe), and a description of how this was done.
The GridFTP protocol extends the standard File Transfer Protocol (FTP) with various useful features such as Grid Security Infrastructure (GSI) security, increased reliability via restart markers, high-performance data transfer using striping and parallel streams, and support for third-party transfer between GridFTP servers. The Globus Toolkit provides one of several interoperable GridFTP implementations. GridFTP is used for all sorts of interesting things: e.g., to download Earth System Grid data, and to stage data to nodes on the Open Science Grid for exexecution.
The UTEP/SDSC work make it straightforward to use Firefox to download data from remote GridFTP (and FTP) servers.