This post is a bit late in coming, but we finally have cross session resumable downloads as part of the download manager that Firefox, as well as any Mozilla Toolkit applications, use. This is all thanks to the efforts of Srirang Doddihal, Edward Lee, Christian Biesinger, and a bit from myself as well (doing the reviews counts, right?).
I’m really excited about our solid back-end for cross session resumable downloads. It is now the case that when you quit or go offline, downloads that are resumable will simply pause, and will be ready for you to resume (or automatically resume) once you restart or go back online. In fact, any download that you pause is actually stopped (if it is resumable), and is resumed when you click resume (we fall back to the old way of pausing by calling suspend on the channel if the download isn’t resumable). So, for those of you complaining that pausing a download, putting your computer to sleep, waking it up, and resuming a download just hangs, you can stop – it works now (beltzner and shaver, I’m talking to you!).
All this will be in the beta of Firefox 3 due out Real Soon Now!
EDIT: Gwah! I lied (I really need to stop blogging about stuff before it cycles for a little while – my track record is really bad!). It will not automatically resume at startup because the code that did that caused a startup time regression so it got backed out. :(