Regulator solution for 5 volts at +2ish amps
You can use an external pass transistor with a fixed 7805 regulator, see for example page 14 of National Semiconductor's datasheet.

It's also possible to use the LM317 to build tracking regulators that can be connected together so that they share the power.

But the reason the integrated packages don't go much above 1A is the dissipation due to the product of the difference between input and output voltages times the current. Switching regulators are much better for higher currents than linears because of this thermal problem.