I've also wondered about this a lot.

Does anybody have any specific places where things like this could be found?

I know some friends of mine use Soulseek...is that a good place to find unreleased Beach Boys songs?

Yes, it is a little discouraging to see tangible stores die, but from what I have observed and read about, the independent record store is surviving, even thriving, in many instances. 
I run a record store here in Indiana and I know of two other independent stores that have opened up withing two hours of here in the past year. 
I think people will always long for pure, honest, tangible buildings to go to not only to interact with others as a cultural epicenter of a community, but to hear and experience new (and old) music from people who truly care about it and provide good customer service untainted by what a giant corporate office or megawebsite is paying them to promote.
Maybe the death of the giant chain music stores will somehow end up being a good thing in that the locally owned and operated record store will rise in prominence. 
Being a huge Beach Boys fan, it's been really great to be able to turn people on to their music, especially younger people (not that i'm old, i'm only 24) who may have only considered them a fun, but trite, band on the oldies station singing about surfing and cars. 
I love playing something like "Surf's Up" and having people be shocked that it's the Beach Boys.