I use All The Deals (http://www.allthedeals.com.au/group-buy-deals.shtml
) which shows all the different deals from the different group buying places - catch of the day, cudo, deal me, living social etc.
So far I have bought one Cudo deal and one Deal Me deal.
The Cudo one I bought was 1m long canvas prints for only $49 each. I bought 2 of them in anticipation of my BIL's awesome photography skills. For the canvases, they sent me an email with a code, and I have a year to use it.
The Deal Me one was a 2 hour full house clean for $45. This one I was emailed with a confirmation number and then had to call the cleaning company to arrange a booking. I rang up last week, and they can't fit me in for another 3 weeks, so I can't talk about what their service was like, but the time didn't really bother me as it was a once off thing anyway - no way would DH let me get a cleaner normally!