I have been using IMSLP for quite a while, but just registered to use the forums and I felt like this would be a good place to start.
I am most of the way through my 5th year as the orchestra teacher at a K-12 charter school. At the end of my first year, due to funding cuts at the state level, the budget for all the music programs was cut in half. While our parent booster organization was able to take away some of the sting temporarily, I needed to look for other ways to provide these kids with great music, and I found IMSLP. The resources on this site have allowed me to continue giving them new, interesting, challenging music that my budget restrictions simply would not have allowed. I was also able to start the tradition of featuring seniors as soloists and add a chamber music class to my schedule with no additional funding. The search functions have helped me find music for even the most unusual ensembles. While I have occasionally had to Finale out parts from a score, the fact that I had a source there to begin with made all the difference, and I hope to figure out how to contribute those parts I have made back to the site so others can use them as well.
I am also the music librarian for a community orchestra. IMSLP has helped us in so many ways, and I don't think it would be entirely incorrect to say this site has kept us in the black over the past few years. The Orchestra Parts project has made it so easy to replace missing parts, or even print out all the parts for a piece and only have to assume the cost of copying them. I'm sure that was (and maybe still is) a huge undertaking, so many thanks to those who gave of their time to make it happen. We have been able to keep our music budget at a fraction of what it was in the past, and it used to be the biggest line item we had. At a time when so many orchestras are struggling financially, this resource has allowed us to keep our ticket prices low and our audience happy at the same time!
I look forward to becoming more connected to the IMSLP community and finding ways I can contribute as well!