Downloader for X seems like a pretty cool program. It seems like a cross between the Mac MSIE "download manager" and Windows programs like GetRight.
Basically, I think of it as an adaptation of wget, with graphical interface that interfaces nicely with Mozilla/Netscape. (This compensates for these browsers' utter lack of sophisticated downloading...) The users can drag and drop links to it, or copy URLs to clipboard (that is, primary selection) and let it automagically suggest to download it.
It also has nice icon. =)
The program was written by Maxim Koshelev, and it's distributed under "Do whatever you want with this, but do not distribute modified the sources without permission"-license. (not exactly open source, but at least Debian has the package =)
The program uses GTK+ widget set, and there's also a version of it that embeds as GNOME panel applet.
The program is also known as "d4x" (which is the name of the Debian package) or "NetThief" (author is planning to change the name - the binary itself is known as "nt" at the moment, which seems to be sort of confusing =).
Home page: http://www.krasu.ru/soft/chuchelo/