Framed or unframed? Or is that part of the question as well? There are a lot of options in a range of prices.

I mounted a board between two windows, even with the top of the trim. Permanently attached to the board are several spring clips used for organizing papers....quick and easy to hang anything you or your kids like at that moment. I have also used little metal clips about 1/2 inch x 1 inch which I attached to the wall with the removable "command" adhesive strips. I used that setup to hang a kitchen towel as a wall decoration. It looks really interesting since you can't really see the clips once the towel is up

If you are not including frames you can use stick glue on the edges and middle of the poster to stick it to the wall. It will then remove easily from the wall and you can wash the remaining glue off. NO mess and no holes

I do not want to use a frame but it is lacking something as is. It is for my 10 year old daughter and I don't want to make a huge investment as I am sure her taste will change soon.

How about backing it with foam core? You can cut it to size with a metal ruler and exactoknife and attach it with spray mount. You could also cut black foam core out to be an inch bigger than the poster all the way around to create a frame-like effect and some depth, then spray mount it to the middle.

You can use poster rails - but even then you're going to have issues with sizing and holes in the walls.

IMO - just get her a box of pushpins from the local stationary store and let her pin her posters & whatnot up to her heart's content - Then when she gets older or moves out for college, plan on spackeling all those holes and painting the room.

I really like the foamboard idea, especially for some of the odd-sized posters I can't figure out how to frame quickly and cheaply

thank you for that great idea.

you could use magnetacks. they are magnetic poster and photo hangers that use magnets to hang up the items so it won't damage them. they are really strong and they are pretty cool looking too. magnetacks website