I am using a 5v Boost Converter, specifically the L6920DB, for my solar charger project. This video demonstrates the most simple circuit you can use with this chip and show the voltage with 1 AA battery and a Lithium Polymer (LiPo) battery. It would work really well with a battery powered Arduino project or just as a charger for your phone.
But if you have a look on Farnell you can find a metric ton of them that all have different features. I chose this because it met my design requirements.
Datasheet – http://www.farnell.com/datasheets/1690388.pdf
The inductor/choke I am using (I honestly tried to understand the difference between a choke and inductor but failed) – http://uk.farnell.com/panasonic/elc09d100f/choke-10uh-2-5a-20/dp/8094756