There's a nice amount of sales here and there and also I've been browsing and doing some purchases here and there - both physical maps (or actually tiles) and printable ones. I've found good ones and also seen little disappointments.
Most notable sales I've seen are going on at Paizo. You get a number of tiles and maps at about 70% off, but the sale ends in a few days so if you want to do some purchases, you better hurry! I've also had two disappointing details about ordering from there - first being the sending takes 1 1/2 weeks, and I wanted to wait for the package to come before ordering more. Second is EU customs reduces that size of orders that can be done without customs hazzle a lot - and shipping cost of 3 sets of tiles is close to the value of the actual tiles, which sucks. While the customs costs would be lower than ordering twice, I really don't want to go to the other side of the city on office hours to queue in the customs office. This second one has nothing to do with Paizo and the first isn't a big issue unless you have reason to use the maps very soon.
Link: Paizo Maps sale
The second noticable place to get maps on discount is Drivethrustuff/Rpgnow. I got Tiles of the dead myself which are very cool, even if I don't have immediate plans of actually using them - I've been itching to run a Zombie game for a while, but whether that's modern, Wild West or Fantasy remains to be seen.
For those interested in 3d terrains Ravenfell looks quite cool, and I remember drooling over it already at Kickstarter, but I've more or less given up on 3d terrains so I'll pass it.
There's also Dave Graffam bundle on sale, which also looks pretty awesome - I've been eying of his models for quite a while but have no personal experience with them. To see the models in use, just google images with Dave Graffam Models.
Link: Dave Graffam bundle
A recent find at drivethru I'd also like to mention is Cemetery Crypts from Heroic Maps - I believe they are the most beautiful pieces of dungeon maps I've seen! They are not on sale but are not expensive either, so if you want to impress your players with cool crypts you should really get them!