Dandelyon's Worlds

There are some business models starting with that. Torn World lets you hand out credits one at a time (which you get for becoming a supporting member: most of your dollars you can thus pass to creators you like). My Poetry Fishbowl has poem sponsorships starting at $5 for the short ones, but you can also just put something into general donations -- it's not rare for me to get $1 or $2 donations and those are useful too. There are some systems where members pay a fee, and it gets automatically divided among the member websites they visit per month; alas, these are just getting started, so not great yet, but the concept is nifty.