Even in 2009, I don't think there's anything simpler for recording and editing sound than an old-school tape recorder. Imogen, her cousins and I have taped ourselves reading books (with improvised sound effects) and yesterday, Immy's almost-10-year-old girl cousin interviewed her.
At the Port Angeles Goodwill, the cassette recorder was $3, the microphone was $2 and brand-new tapes were $.29 each.