As a donation or source of loan funding ?
Donation would be straight forward. Donations to a 501(c) blah blah blah are very normal.
As a source of loan funding would require continous re-implimentation of paid back loans, otherwise paid off loans would then revert to some limbo. If it were a substansial amount, you could create a trust, pay someone to oversee the trust, and fund loans according to your wishes. For instance, only loans for rooster breeding in the Philippines .... just kidding
Kiva might be able to handle your wishes, try the contactus email.
Realisticly, you would want to balance a donation and loaning such that it is sustainable. Since interest free loans are inevenitably going to lose money (defaults ..) and if you make a %10 percent donation out of each loan, in ten years you would have no money left to loan. Perhaps that is ok - you might want to envision what you want to accomplish .....