Recently Jonathan de Ferranti completed his global 3 arc second elevation data set and he has now also made available a reduced resolution version at 15 arc second resolution (that is 86401 × 43201 pixel) in 24 tiles for convenient use on low resolution maps on his Digital Elevation data page. For finding the tiles you need in the full resolution data you can also use my DEM search tool.

There are still a number of smaller errors in this data but anyway at the moment this is by far the most uniform quality global elevation data set available at any resolution.