I have two methods of finding ways to get involved.
1- Ask friends what they do.
2- Search the internet for organizations in my area; ex. I Google "homeless shelter mycity", "food pantry mycity", "animal shelter mycity". I'm experimenting with sites like VolunteerMatch, but I find the listings aren't always up to date, and organizations don't always respond.
I've learned some tricks for those who do homeless outreach on their own as well. Sometimes a city has a "day labor center" around which homeless workers gather, camp, and try to get any work they can. If you have supplies, this may be a place you can distribute them.
So. Friends. What do you do?