Here's what I did...
I store mine by folding them in a zig-zag pattern (back, front, back, front) and then securing them with a large bull dog clip. We have put a few hooks up in various places where we tend to hang the pennants from to make it easy to pop them up. If they aren't long enough to go where you want them to, I use a piece of string on each end to lengthen them so they fit across the area I want them to. I have even cut them for a super duper special occasion to fit, as its easy enough to sew them back together when its all over.
I love my pennants and think they are great value for the time and cost it took to make them!
Green-ness: 5/5 for repurposing material and not needing to buy a disposable product ever again.
Frugal-ness: 5/5 for buying from an op shop or using material from your stash.
Time cost: Around an hour for me from go to whoa.
Skill level: Sew and cut in a straight(ish) line skill.
Fun-ness: Great fun to pull them out over and over for celebrations! They get a specialness about them after a while!