So have you ever been out hacking portals, and your XM levels are too low to do anything? That last portal you recharged took the last of your XM and you can't wait the 20 minutes for the portal to recharge?
Well I stumbled upon a great place to get a fair amount of XM. It may even be as good as an unclaimed portal or a level 1 portal.
What is this great source for XM, you are probably asking?
Your neighborhood cell phone retailer. Add to that every strip mall seemingly has at least one. Each retailer has hundreds of XM there for the picking.
Just a quick tip that may help you.