In addi­tion to the gift econ­omy, Chris Ander­son of The Long Tail describes the three other busi­ness mod­els in today’s ‘free’ econ­omy.

Paid prod­ucts sub­si­diz­ing free prod­ucts
Pay­ing later sub­si­diz­ing free now
Pay­ing peo­ple sub­si­diz­ing free people