I'd enjoy seeing specific activities/events that attract players to certain areas/activities.
"For the next 24 hours all experience gained on caravans is doubled"
"Ghouls will give double experience for the next 24 hours"
"A rich vein was struck at Broken Hills! Miners will mine twice the ores in the same time for the coming 24 hours!"
"V15 has been infested by a rather rich raiding party, loot will now spawn every few minutes for the next 24 hours"
"A strange air hangs around modoc, giving players experience (+500) for every minute they spend there"
The above are just examples/possiblities, be creative.
Of course such a thing would require a bit more work to set up than doubling all xp, but I believe it would be a nice way to get players to come together, either to converse/coop or blow eachothers heads off.