Using a Macbook Pro alongside an iMac
Using your mac in target display mode would waste it's potential as a more power computer than your MacBook. Try an app like Teleport. It lets you network your multiple Macs together so that a host Mac's mouse and keyboard can be used to control other Macs. It works very similarly to multiple displays on a single machine, and even the clip board is shared between the two! The only issue is that you can't drag windows between the two displays (which are actually running on two separate computers), but at least both Mac's power can be used.