Ask HN: Looking for feedback on my rate (iOS/Android)

I'm currently a junior studying computer science but for the past year and a half or so I've been doing a decent amount of short-term mobile contract work.

Here is some of my previous work:

* Venmo for Android - https://market.android.com/details?id=com.venmo

* Wolfgang's Vault for Android - https://market.android.com/details?id=com.wolfgangsvault.concertvault

* Battlestar Galactica Bobblehead App - https://market.android.com/details?id=com.laan.BobbleFanSyFy

* Philadelphia Concert Hub for iPhone - http://itunes.apple.com/us/app/philadelphia-concert-hub/id315859665?mt=8

I'm wondering what I should charge per hour.

I'm thinking of raising my rates for new clients but thought I should check here to see if anyone has any input.

Sorry for such a vague question and for not listing my current rate, just want to see what answers I'll get to see if they match what I'm thinking.