Expedia.co.uk is currently running a refer-a-friend promotion whereby you get a £20 off voucher on a hotel booking, no minimum. At least in New York, there are some hostels that are less than 20 quid so you could end up with a free bed! Now it's only one voucher/booking per e-mail/credit card but I know T-Punks are a creative bunch and will find a way to make good use of this.
If anyone would like to be referred, please PM me your e-mail address. As a caveat, I get a voucher in return too but I'm unlikely to even use them because I'm spending all of my time this summer in Canada.