You can get good looking stickers at a place like Kinkos, get your design ready, ask for sticker paper, (like Crack n Peel) and then just copy it onto the paper. Each copy will cost less than $1.00 and you can get around 16 stickers out of each page depending on the size of your sticker design.
For poster making, get your image ready in black and white then blow it up with a copier or projector as large as you desire, then reproduce the design on xerox. You can also try silk screening or printing but it's way more expensive. Silk screening requires screens, photo emulsion and ink. Offset printing is pretty convenient for runs over 500 units but it's also expensive. For all of you interested in making and pasting your own posters, the easiest way to paste is to buy wheat paste (try All in Onebrand) also called wall paper paste at your nearest hardware store it will cost around $2.00 - $5.00 a box, you'll need a big brush (4" or 6") and a bucket, soak surface, place the poster then brush the poster hard enough to avoid bubbles. You can also MAKE paper paste from scratch for practically FREE!