Ashenvale

From Azshara you hop onto a rider and fly to where the entrance from Northern Barrens to Ashenvale is. There you find the horde fighting the Night Elves at the border. After a few short quests, you are sent to Splinter Tree Post.

You do the quests in Splinter Tree Post, and you wind up at a tiny quest hub near the border to Azshara. Once you complete that, you are sent to another quest hub at a recently discovered volcano in Ashenvale, which has already erupted. There is another quest hub North-West of the volcano that has you bomb Astanaar and do some quests around the remains of the lake surrounding Astranaar.

Before you leave Ashenvale, be sure to hit up Zoram'gar, which is now a minor quest hub and outpost of the Horde. I made sure I hit up Blackfathon Deeps and solo'd it, managed to do it with relative ease and only 1 wipe getting all the quests completed for a 100% clear.

This area lasted me until about level 28. You are quickly shuffled off to Stonetalon Mountains which is where I headed next. Not alot of changes in Ashenvale however, mostly the new quest hubs, the Alliance & Horde fighting, the volcano and Astranaar.