Last minute trades aren't as widespread as I would have hoped, but there are some areas with a good amount of inventory.
[Disclaimer: This is looking at August/September inventory - things could be very different in other seasons. Perhaps I should revisit this once a month to get a year-round picture?]
45 days from now is September 25th, and if I look at everything available from now through then, there are 1054 resorts. If I restrict the search to just places with 2BR, it's still 440.
From there, looking by region:
Africa and Middle East is fairly sparce. South Africa and Egypt look like the main places you could pick up "last minute", but most of those resorts only have availability 38-45 days out. If you want to pick any of those up, it would probably be best to grab them right at 45 days.
Asia is fairly sparce, too. India is the main country with a lot of last minute inventory, and likewise most of it is 30-45 days out.
Australia and New Zealand is even more sparce, but what is available appears to be more evenly distributed. Planning right at 45 days wouldn't be as essential.
Canada has almost no last-minute inventory, and half of it is at 45 days out.
Central America is the most sparce right now.
Europe basically only has last minute inventory in the Canary Islands, Finland and Sweden. A fairly good mix in those locations, but most of the inventory is 30-45 days out so this is one you would want to book pretty close to the 45 day window. Anywhere else in Europe wouldn't work well for last minute.
Mexico seems to have good last minute inventory.
South America is relatively sparce, with most of the last minute inventory in Argentina, Boliva and Brazil.
So outside of the US, the most reliable places to pick up last minute inventory appear to be Mexico, South Africa, the Canary Islands, Scandinavia and Argentina. A few other places might be hit or miss. In most places, there's a good chance you won't find anything when you want it.
Inside the US, the most reliable last minute inventory is in Orlando. You can even get into some of the nicer resorts sometimes. (Right now, I see 2BR units in the next 45 days for Wyndham Bonnet Creek, Orange Lake East and West and Sheraton Vistana.) I suspect that you could almost stay year-round in Orlando with last minute exchanges, except perhaps a few holiday weeks.
Texas (inland) has good last minute inventory.
Hot Springs, Arkansas also has good last minute inventory.
One surprising area that has a good selection of inventory is Kauai. There's something available just about every week.
Colorado, Phoenix and Salt Lake City have some last minute inventory. It might be a little too sparce to rely on, though.
So inside the US, it looks like the best bets are Orlando, Texas, Kauai and a few other spots across the middle of the country.
Not the best variety, but there are some places that appear to have consistent last minute inventory. It's hit and miss in many other places, but someone who was flexible (can take off anywhere and can either drive or can fly cheaply) could probably have some good success with an ongoing search.
