Drive Genius presumably is able to resize partitions, but is somehow pricy. I haven't used it, and as with all such pieces of software -- make sure that you have backed up all you data before utilizing it.
This said, if you have an extra external drive you could backup the second partition to an image or partition on the external drive using SuperDuper! or Carbon Copy Cloner; then repartition the original drive and restore the system from the image that you've created at the first step. If you have Time Machine backup, you could use that to restore, although I think it is slower.
Again -- whatever you do, make sure that you have a backup of all data.