The charitable definition of "donate" implies giving money without getting anything back (except a good feeling).

On my site, I use these divisions:
Donate = giving random bits of money in appreciation for my blogging so I can do more of it and/or giving small amounts of money less than a whole poem's price.
Sponsor = giving enough to fund publication of a whole poem.
Different levels of support get people different perks, so sponsors get the most.