Sometimes last minute travel deals are absolute steals. Even though my life isn't really well suited to spontaneous trips (work, house, pets - my carefree days are behind me) I'm still subscribed to way more travel mailing lists than I should be...
While I'm going to mainly talk about New Zealand-centric last minute travel deals below, for international readers, there's always Lastminutetravel and you most likely have your own country-specific versions!
Last minute flight deals
Grabaseat is the home of cheap seats on Air New Zealand flights. I wake up to emails from them every morning, but it's probably best to follow them on Twitter as well!
Last minute hotel deals
I've used these a few times before, specifically for staycations. I do like the idea of the mystery deals, when you book an amazing discount on an unknown hotel that's revealed AFTER you make the reservation. If you're willing to put in the time to do some sleuthing, though, you may very well be able to deduce what the hotel is based off the information they do provide about their facilities/location! Lots of websites offer these - I've mainly used wotif.com.
Last minute rental deals
One thing I have yet to do is take advantage of a car relocation deal through the likes of Transfercar. They're great for backpacker types with flexible schedules. When visitors rent a vehicle (a car, a campervan) and drive one way from one end of the country to the other, someone has to bring it back! And that could be you, if you can arrange your own way there. How it works is that you pick it up, have a set amount of days (and kilometres) to drive it back to the home base, and pay nothing or very little for the rental. Sometimes fuel (and ferry fare if it's interisland) may be covered too. To be fair, you won't really have time for sightseeing but if you're on a super strict budget, it's not a bad option.