Ask HN: How can authors (musicians, developers, etc.) encourage donations?

I was just reading a story about WinAmp and how people literally sent money in the mail (back in the day) to pay for the app even thought it was shareware. Have attitudes changed that much since the '90s or is there an art/science to encouraging voluntary financial support?

I'm curious if anyone has any personal examples (or know of any published stories on this subject).