Guilds are often involved in making charity quilts and I am sure your local quilds would be happy for donations. Alternately you might be able to sell some fabric at their annual garage sales. Call and see if they have a sale and ask about renting a table. First I think you should do a lot of sorting perhaps into 3 categories: keep, donate, sell.
Good luck. We all have this problem but in varying degrees. I keep making and try to buy NOTHING but my stash does not seem smaller at all.