I downloaded Ovia Fertility today to begin charting my temperature and CM to find my fertile days better. Hopefully it helps. This was only our first month trying, and since it looks like we may take awhile to get there, I want to start charting long before we reach the 6 month mark of trying.
I picked this app because at least one friend is using it to chart her preganancy and also because it's Free!

What app do you use?
What experience do you have with this one?