How do you strengthen your hip flexors? (Page 2)

I used to have hip flexor soreness but found as I got fitter and did more running and cycling they got stronger as my training load increase and now they don't give me an issue.

Could it be just doing more training in a smart way will help them get stronger?

I second (or is it third or fourth) the Powercranks suggestion.  I have them and they definitely strengthen your hip flexors.

I have notoriously weak hip flexors that rear their ugly head almost every marathon I do. 

the cheap way I've strengthened them is using a versa-tube and doing high knees (mimicking running form) with them.  this was very effective for me....or was it affective for me..I can never keep those 2 works straight...