you can list your free plants on freecycle.org
you can take divisions to work. Most plants disappear at my work place without a problem. Seeds would not go over there.
you can take them or seeds to our local garden group if you are in one.
you can sell plants on craigslist. I find people will buy in May and no later and they want things that are in bloom at that time. Which is limited.

swapping I've found is an art form. Selling and giving are actually easier.

Now for cheap buys-check your master gardeners and local plant sales usually in May. $3 buys a nice division or even a shrub/ tree!
karen

Thanks Karen! Somewhere in a GW thread I read that local groups/communities designate an informal site like a picnic table in a park pavillion, public building or farmers market to rehome extra plants or seeds. Before I posted here I searched the Garden Clubs of Illinois website. (Nothing local - mostly northern Illinois.)I tried the U of I extension, Illinois Gardener, Craigslist... I finally found the public parks system website listed "Garden club at senior center, 1st Monday of each month, 6:30 p.m.,fee $15.00."

My first thoughts were "Oh no, who can afford $180/year membership. This probably isn't for me." I went anyway...glad I did. (they have since changed the wording to "annual fee".) I met some very kind, welcoming women. I've lived/gardened in this town most of my life - never knew there was an annual plant give away/fund raiser.

I found out that there are many local groups affiliated with Garden Clubs of Illinois. Why doesn't the Illinois site list the various districts, clubs or contact info? My e-mail to them was shunted from club secretary to commitee chairperson, who was willing to forward to my local membership chair...by then I'd already joined.

Anyway, to anyone with the intention of easily swapping, buying, or giving away plants/seeds locally your suggestions were spot on. Freecycle/Craigslist, co-workers, garden clubs, mastergardeners, and plant sales are the best options. Information about the last three take some ongoing searches as they don't advertise thier activities much.
DD