I have 9 referrals, one is already maxed out and of the rest only one is active but I still get 1-2 $5 gift cards a month. So basically I spend my gift cards as soon as I get them and can never save them up lol!! That is awesome that you've been able to earn so many Megan!
So if it was me I'd go for the Kindle (I am a huge reader!!), an iPod or something photography related even if it's just something small like extra CF cards, a high speed multi-card reader, reflector, small backdrop stand, white balance card, umbrella kit or even a few books. The student/teacher version of Lightroom 3 is high on my list as well. Also I would love to have a Shark Steam Mop or something similar for my tile floors. Also what about a favorite TV series on DVD or some fun kitchen gadgets??