I have no idea if wine plays into your wedding theme, but with it being in Sonoma there's a good chance.  What about plastic top wine corks and bagging up 5-10 or so per guest, they are .15 each but rather than leaving the top plain do a monogram or both of your intials on a round sticker and affix them to the tops.  Also any decorative cork would be cute but they are usually 10.00+ each.

The Cork Store – Plastic Top Corks

I just made a mobile for a baby shower gift for a dear friend of mine…but as I was making these funny little birds, I thought what great wedding favors they would make! I made them using a soft white linen fabric with colorful (various hues of pink!) and strung them on strands of crystal to hang from the ceiling. I filled their bellies with dried lavendar. Bird themes seem to be pretty popular for weddings right now.  Using single ones at each place setting …or suspending them from an arrangement of dried branches on one of the reception tables seems like a touch of whimsy that lots of brides are looking for! (Not sure if this photo is going to work…so I've included a link.)

http://www.flickr.com/photos/24829115@N02/2489740467/

Believe it or not, I found some cute stuff at Wal Mart and shops like Hobby Lobby. They have nice looking lace-type things and bubbles and things like that you can do yourself.

Here's an article for some more cheap tips if you are interested: http://www.ehow.com/how_4704067_plan-cheap-wedding.html

I agree with Jeannine.  We are making a donation to charity.  When on a budget, $1.50/guest doesn't go very far, but if you multiply 1.50 x total guests, you can really make a meaningful contribution.  Create a flat card on a good cardstock to let guests know about the donation – “In lieu of traditional favors… etc.”

You would be very surprised how much retailers are willing to work with you and negotiate prices these days, even online only retailers.  If you have a particular wedding favor in-mind, do an online search and email the retailer saying you are on a tight budget and ask if they would give you any discount on your order.

This actually worked for me…one of my favorite candle makers in Ohio gave me 25% off by just sending an email!

If your per person budget is less than a few dollars, I agree with several of the other replies above.  Make a donation to a charity that is meaningful to both you and your fiance.  Use nice, heavy cardstock and print out “In lieu of a wedding favor, we made a donation to support….”  and why the charity is important to you.

Hope this helps!