Thanks to one of the more detailed maps of the Free Cities that appeared today, I have managed to assemble a very rough speculative world map.
Obviously, Westeros is in the west, with the Free Cities immediately across the Narrow Sea to the east. Further inland is the vast Dothraki Sea and the city of Vaes Dothrak. South-east of there lies Lhazar, land of the lamb-men (where Daenerys hatched her dragons), and further south is the forbidding Red Waste and the great trading city of Qarth on the entrance to the Jade Sea.
Note that, whilst much of the coastline and in particular the area around Qarth is totally random, the distance from the Free Cities to Slaver's Bay is accurate. I also based the far north-eastern coast of Essos on screengrabs from the Game of Thrones TV title sequence, which shows the coastline beyond Vaes Dothrak. I also included the Summer Isles (south of Westeros) and the Iceland-like island of Ibben in the far north. Not show are Asshai and the other lands of the Jade Sea. In addition, I based this map on the 'Jade Sea = Indian Ocean' school of ASoIaF cartography rather than the 'Jade Sea = Black Sea' school, pretty much for no other reason than I felt like it.
So there you go. It'll like be some years - if ever - before a full and official map of the world emerges, but this should hopefully make things a little clearer.