I'm not so sure about programs "like limewire" but I would offer you some advice, based on my experience with file sharing.
Nowadays, most things you are looking for will be available through torrents. If you are looking for music you can check out http://www.mp3raid.com/.
You can only download one song at a time so it's not easy to get entire albums, but I find they often offer music that's rather hard to find other places.
I also use a program called DC++ to download some things. There are many variations of the program, as it is open source, but it works a lot like limewire or kazaa except instead of being one large network, you can join any number of rooms where all the members there share what they wish. It is a bit harder to configure but it can pay great dividends as you can also chat in these "rooms" and connect with other collectors.
Finally, when all else fails, I use rapidshare. It will cost a monthly fee to use so what I do is wait until I have a long list of things I can't find elsewhere and mass download it in one month.
Hope this helps.
