I do these at work all the time - and I love to bake now - so it is a good match for us.
I bought a bunch of the little 4" springform and regular baking pans to do small pineapple upside down cakes and cheesecakes. I use parchment on the bottom and once baked and cooled, wrap them in shrink film or slide them in a ziptop bag and freeze. The day of the event or the night before take them out and put on a small 5" cardboard round with either shrink film or put into a small box. They look like tiny versions of the originals and we can get 4 or 5 dollars a piece for them.This is something I do over the course time so it's no big deal to pull them out and defrost.
As a matter of fact, I do these for Christmas gifts too for people at work in a small pretty box and they seem to get good reviews because people drop a hint of what kind they want every year. If you want the recipes for the good to freeze cheesecake or upside down cake PM me.
Other items: muffins (anything with a crumb top), small caramel apples, small candied apples, caramel/choc pretzel rods with quins, seasonal breads (those freeze well too!), flashy cut out cookies w/ royal icing (also good ahead of time item), petit fours, and don't limit yourself to traditional baked items. Small gift sets go too! I am getting ready to do the decorated sugar cubes with a package of tea - we put these in a clear box (Michaels has them) and with a piece of ribbon it's a perfect take away for some people.
Cookies in take out boxes are also fun and you can put a label of your group on it.
Oh and we do mini pies - 4-6" premade shells with fillings - they sell for $5 too.
Also, don't forget diabetic/sugar free-reduced options.
I always do something that is specifically reduced and provide a little card with info on ingredients etc. That way if anyone says I can't or I am on a diet there is something there you can tell them about before they make their get away....
AND we mark items with either nut/allergy disclaimers or have a little sign saying products are made on equipment not free or allergens. You would be surprised how many people are appreciative of that - oh and gluten free items as well. A lot fo kids and adults can't have certain glutens and when they find an item it's like they hit the jackpot.
Ok, so I rambled....lol

We do these 4-6 times a year and merchandise the stuff up - people look forward the the booth and we make good money on the items. I want to say the last one was $675 for a 3 hour booth with donated items. Our mission is a fiver - anyone who stops can choose an item or a group of them for $5 - no one leaves without dropping the five usually because if you are spending 4 you might as well spend the $5. LOL
Hope this helps and I think the key is people eat with their eyes first so if you merchandise your stuff well you can actually charge a bit more and move things really fast. Invest in some little boxes, clear clamshell containers, or of all things - chinese take out containers (100 for $15 at rest supply).
If I remember anything else I will pop in to add it.
