Mages are great they have those lovely portals to all the major cities and we're all dead jealous, druids and death knights get a taste too with their class portals to Moonglade and Ebon Hold respectively. But the rest of us just have to rely on our mounts, flight masters and boats or zeppelins (depending on our faction) or do we?
I'll admit that many of these portals are level dependant or rely on quest chains being completed, but to the savvy (or lazy?) level 85 most if not all options should be available or can be had quickly if they're not. I apologise in advance for the slight Alliance bias but I don't yet have a level 85 Horde. /hangs head in shame.
Shattrath and Dalaran
Heading to Shattrath and Dalaran there are portals to Stormwind and Orgrimmar but sadly these are a one way trip deal only. Shattrath and Dalaran also have a link to the Caverns of Time making either city an alternative hearth point if you raid Dragon Soul. Instead of a portal though you need to speak to NPCs, In Shattrath use Zephyr, found in the World's End Tavern in Shattrath's Lower City, once honoured with the Keepers of Time and in Dalaran you need to speak with Zidormi (or use the portal behind her) and no reputation requirements exist :
Besides the flying taxi/zeppelin/boats that link our major cities, there is also the Deeprun Tram that links Stormwind and Ironforge:
Darnassus and Exodar which I wrote about way back when
Silvermoon and The Undercity
Hellfire Peninsula side there is now a portal back to Stormwind / Orgrimmar, I don't know when this got added but the 2 things I know are that it wasn't a working portal in TBC but it IS now!:
Un'Goro Crater and Sholazar Basin. These are activated by completing a quest chain (only 8 quests) beginning with the Avatar of Freya. The starter quest is The Lifewarden's Wrath and shouldn't take long to complete and is well worth the effort if you're stuck in Northrend and wanting to get back to Southern Kalimdor:
Wintergrasp, you can port there from Dalaran and then fly manually the short distance to the waygate in Sholazar Basin. There is also a convenient return to Dalaran from Wintergrasp meaning you can use this as a shortcut back to Dalaran too: