I Decided to reveal what i did to get from level 40 to level 50 in a relatively short amount of time.

Level 40-44

Head over to Tanaris and kill the Wastewander Thieves. This is the most efficient levels i have ever made, because you can turn in 5 Wastewander Pouches that the thieves drop fairly often in bunches of 5 to npc in Gatzegan to get 480xp, on top of all the xp you are gaining from the thieves. I only killed thieves at lvl 40-42 (only the bandits and thieves). Here is a link to exactly where i leveled off them-http://i44.thottbot.com/m/b/wow_81522.jpg- the white boxes in the left corner is roughly where i was. Among the Pouches, they drop mageweave nearly everytime in increments of 2-3, a stack is worth around 1g on the Ner'zhul Server! You can also find solid chests around the thieves.

Level 44-48

Stay in Tanaris and head to the Southsea Pirates by the docks in eastern tanaris-http://thottbot.com/?m=7077 However, if you are melee, stay away from the Swashbucklers because they can disarm you. I went inside the dock gates (not by the campfires) and i killed around Andre Firebeard's area (not near him though :hes tough =p:) These also drop mageweave and solid chests spawn around the pirates for some mighty good 'ol treasures.

Level 48-50

Head to central Tanaris and find the Dunemaul Ogres here-http://thottbot.com/?m=39759. The Ogres drop good loot to NPC that sell for over 1g each. Solid Chests can also be found among them. On the northern end, there are a bunch of ogres in a line, and you can kill from the beginning to the end just as the first one spawns again, so you can kill them infinitely without ever having to stop, which is what all we crazy grinders like to hear =p.

While i did this, i found 2 epic drops, Dazzling Longsword and Gut Ripper, over 120g worth at the AH, as well as the Schematics for a Sniper Scope in a solid chest. I hope this guide can help you level from 40 to 50 with relative ease, Good Luck!