Pre-package volunteer programs organized by for-profit companies are increasingly popular these days. Though this category doesn't include the Peace Corps, which has a different structure and is not-for-profit, such programs often appeal to Returned Peace Corps Volunteers who want to serve again but aren't able to put forth another two-year commitment.
The UK Guardian newspaper ran an interesting article reporting on criticisms leveled by VSO (roughly a British counterpart to the Peace Corps) against such programs.
It is not feckless hedonism or misplaced idealism that VSO is criticising, but the booming industry in pre-packaged volunteering programmes. These are often run for a profit (although badly organised non-profit-making schemes may be just as harmful). "This is a growth industry and very competitive so the objectives may not be to deliver the maximum benefits to the communities these young people are working in", says the UK director of VSO.
The article suggested that anyone interested in such programs consult EthicalVolunteering.org or related sites to make sure the program they choose will actually do good.