EDIT: Apparently, this potentially has been fixed within the INGRESS game last night and will issue an immediate cooldown. Sorry folks. Post explaining updates
Ingression recently posted an article discussing an exploit that allows you to get multiple hacks off simultaneously before hitting the cooldown mode for a portal. Quite simply, you click hack on a portal and when the "hacking..." screen pops up, simply click off of the screen to get back to the portal screen and click hack a 2nd time. Repeat this process before the first hack completes to beat the cool down. If hacking an uncaptured or enemy portal, this will net you AP as listed in the AP & Leveling Guide as well as items. This exploit takes advantage of slow network connections as the cool down status doesn't take effect until the first hack has completed processing on Google's server and updated your scanner.
Read the full article at Ingression's site.