Just started playing dwarf fortress again and had an idea similar to this, so naturally I checked to see if someone had already done it, and found the project moving pleasantly along. Since you are looking for ideas and whatnot...
First, you have several development possibilities available. It looks like currently you are cranking out better functioning versions and let volunteers procure/produce all your sounds (which is what I recommend) and seem to be getting decent progress, and a few extra soundpacks to boot. If anything, try to focus on the core soundpack before all else.
Also, it currently seems that you are assigning roles for certain sounds/etc, but your page at
http://www.krauselabs.net/dump/todosounds.htm does not currently list who is taking what role, and the bug page at
http://df.zweistein.cz/soundsense/mantis/view_all_bug_page.php seems like it might, but is a bit hard to dig through. By the way, assume those that visit this thread can help with development, and edit your first post to>
A: Include these links for development purposes;
B: Include a list of people currently assisting, including who to contact to offer help (possibly with info like tyrspawn's message);
C: List formats that are acceptable for contributions, filesize limitations, etc.
D: Other stuff not directly related to functionality that you need assistance with- art, hosting, etc;
Another alternative (taking the to-do page for example) is to allow file uploads for the missing sounds specifically (with some limitations, see below) and enable a testing/voting system for them. You can choose a number to keep based on rating from voting for the official soundpack, and might get original works contributed this way (though you might have to assume the worst and test every uploaded file for copyright issues, or at the leest have a 'copyright infringment' removal process that users can use to state infringements and remove). In this case, it becomes more of an open-source effort, and you can even possibly open up the entire soundpack for suggestions this way and include high rated submissions.
I might have more to add later, admittedly I still have yet to test it (downloading it now, just got intrigued by it and read through all the pages of conversation). Might be time to break out the MIDI editor and go to town
[Note, for other ideas: My original idea on this (without thinking HOW I would actually do it) was basically playing different music files based on seasons, events, and fortress status. I was thinking each season would have a base theme that gets modified for fortress wealth, seige status, dwarf mood problems (with an 'unhappy' theme for a fortress full of unhappy dwarves), and possibly landscape (sinister, etc) and z-levels dug/underground features exposed (more cavernous).]