My sister has just started working out and has lost 20 pounds so far. I'm so happy and want to support her with a really cool fitness-oriented present.
My first idea of getting fitted for tennis shoes crashed and burned because I found out she just bought tennis shoes.
Personal trainer session
New gym bag filled with little goodies like socks, hair bands, towel, water bottle, etc.
iPod shuffle (they can be had for around $40) with an iTunes gift card
A good lifting book like New Rules of Lifting for Women
A series of classes somewhere - yoga or pilates or kickboxing - whatever she's into
Subscription to a fitness magazine
Exercise gear she can use at home if she wants - like a swiss ball, a mat, resistance bands
That's all I can come up with off the top of my head ...
ITunes gift cards or a small iPod she can use while exercising.
Small workout gear (resistance bands, kettlebells, etc)
Workout outfits, if you know what she's comfortable in.
A heart rate monitor, depending on your budget...
Photochick had some great ideas. How about something for a post-workout, like a massage. They are cheap all over. My friend got one for an hour and a half for 50 dollars. I couldn't believe it. There are really great cookbooks for people trying to eat healthy. New water bottles are great. I am an avid rollerblader and going with a pair of K2s is never a bad investment. My legs never looked so good. I know that when I work out all the time, I tend to ignore my hair. I would have loved an hair salon gift certificate or something like that to reward my hard work. Everybody need supportive sisters like you.
Thanks so much guys! The program she's gotten into involves a lot of different types of classes in addition to weekly personal training. It's just cool.