Fractions are going away in 2nd grade according to the CCS. However, my district is still balancing CCS and state standards. State standards for 2nd grade still include fractions, and students are still tested on them, so we covered fractions back in November and periodically review the concepts.
A few months ago I heard about Front Row Education, I believe from a Teachercast podcast. Their fraction app is in the testing phase and my students are lucky enough to be trying it out. The app provides a progression of fraction skills linked to the CCS, starting in third grade. There are multiple choice questions, fill-in questions, video tutorials, and written explanations for each level of fraction skills. Due to the age/fraction knowledge of my students, most of them only progressed to about level 10 in the app, but there is a lot more learning available for them.
The teacher dashboard is well organized and provides a whole class snapshot as well as the ability to drill down and see exactly what each student understands and struggles with, all tied to CCS.
My students liked it so much (much better than workbook pages and differentiated and self-paced) they are hoping for more math topics at some point in the future.
For more info about Front Row Education you can reach them at email@example.com and there's a video at http://www.frontrowed.com.