I don't find the PVE especially stale, and sometimes I like just sort of mindlessly doing events and killing mobs for hearts. But it sounds like you want more company. While most of the server has moved beyond those zones, if you pick the Human zones I think you'll have more chance to meet other people. So that's Queensdale, Kessex Hills, and Glendarren Fields. Since you scale down to the appropriate level, it doesn't matter that Queensdale is a 1-15 zone, if you haven't done it, you'll still get decent exp.
If you're working on a zone, try to get the 100% completion bonus for it, as that gives you some nice stuff at the end of the zone (which you probably won't be able to use...).
In addition, there are frequently PVE events like Prissy's map clears that occur twice a week. You don't have to go to an entire event, and you don't have to make every one - just going for an hour or so will get you some good experience. Right now she's in either the 1-15 or 15-25 zones so you definitely could go to those.
Don't neglect gathering raw materials & exploring: both of these activities give good experience. Sometimes when I'm tired of killing stuff I've decided to see how much of a higher-level zone I can clear for fun. Most of the mobs run pretty slowly. :D
I also recommend crafting. Since each profession can gain you 10 levels, you can get a couple of levels easily by leveling either cooking or jewelcrafting and one of (tailoring, leatherworking, huntsman, artificer, armorcrafting, weaponcrafting). The good thing about jewelcrafting and cooking is that they use different materials from the other 6 professions, so both of your crafting professions are competing for the same fine materials. If you're just trying to powerlevel a crafting skill, there are a number of guides to show you what to make, so you can shop ahead of time to line up the materials so that when you're at the crafting station it's just go go go!
WvW events can also be a fun change of pace and can sometimes get you over the hump.
Whatever you do, try to use buffs: food, potions, tuning crystals, sharpening stones are all pretty cheap and the effects from having a food + other buff can really help. In addition, if you have any boosters from chests they can be great to use (don't forget crafting boosters when you're going to do some serious crafting).