My favorite way to repurpose my girls' jeans is to make a cute new pair of boho style jean cutoff shorts. When their jeans get too short and too tight I've found a way to get one more season out of them by making jean cutoffs with an extra strip of fabric down the side!
How to Make Cutoff Jean Shorts with a Strip of Fabric
1) Cut off your jeans (you can always cut these again a little shorter later, so I usually keep them a bit longer to start with)
2) Seam rip your sides. Up by the hips you'll probably find a lot of extra bar tacks and zig zags, just keep seam ripping. Have patience. When you get to the waist band, you'll need to cut through. (If these jeans still fit great in the waist and hips, but are too tight in the legs, check out this blog post for adding more room in the legs only "How to Make Your Skinny Jeans into Boot Cut Jeans")
3) Pick your favorite fabric and cut strips as long as your new shorts from waist to cut off edge, and as wide as you need to make the shorts fit comfortable plus seam allowance.
4) Sew these strips in right sides together. I like to taper in a bit up by the waist for a more flattering and comfortable fit. Be careful for any metal rivets (usually near the pockets) These guys are notorious needle breakers.
5) If you want your new cutoff to have a raw edge, I like to sew a straight line about 1/2" up to keep a tidy fringe, without an excess of unraveling.
These are so easy to make! You get to decide how short you want them, what color fabric to add, and how much wider they need to be to fit comfortably. I also feel like this is a pressure-free sewing project, since these jeans are already useless, you really have nothing to lose!
Some more fun and quick clothing alteration DIY's you may want to check out Easy 3 step T-shirt to Tank Top DIY and How to Turn Your Skinny Jeans into Boot Cut Jeans.