Connect my Pi model B to mac USB port. The power LED remains off. There is excessive amount of heat generated at the component highlighted in the pic. Any idea how to resolve? http://i.stack.imgur.com/aWNxg.jpg
I think that component is an LDO regulator. It getting hot might indicate excessive voltage from your supply.
It is also near the F3 polyfuse (look underneath the board toward the corner, you'll see the F3 label).