General ideas:

bulletin boards, windows, ledges, storefronts, walls, tables, events, hallways, kiosks, flier-friendly-business, mailing lists, poles, etc

Specific ideas: 

the public libraries, campus buildings (the quad, english building, psychology building, campus libraries), Red Herring 

World Harvest (JOR), Douglass Branch Library, IDEA Store, Aroma Cafe, Cafe Kopi, Jane Addams Bookstore, WEFT, Dandelion, The Drum Shop, Pekara, Exile on Main, Convention and Visitors Bureau, Merry Anne's, Big Grove Tavern, 40 North, Springer Building, Champaign Public Library, Panera, Starbucks, UPS Store, Espresso Royale, Atlanta Bread Company, Arby's, Sweet Indulgence. Urbana Free Library, Strawberry Fields, Lincoln Square, Common Ground Coop, Art Coop, Mail info table, Wind, Water and Light,

Supplies you might need:

thumb tacks, tape, wheat paste, stapler, staple gun , etc

-Be sure to ask business owners for permission first