We call this pro-bono work--donated time and expertise to causes (or sometimes just people) we believe in. Is it valuable? Of course. Is it a good thing to do? Certainly. But it's pretty solidly on the "handing out fish" end of that classic analogy.
*Note: I'm not currently accepting freelance gigs--building Purpose Portfolio has me pretty much at capacity :) Thanks for your interest, and feel free to drop me a line if I can help find the right designer for your project. `sj