Siege is where you'll probably find the most stuff outside bandies and pots up for grabs, but if you are dead set on Standard Production shards like GL etc...
Pretty much any of them with a active PvP/Spawning scene have potential. Take some time to observe folks, find out the odd times when small groups like to sneak in spawns, I've had my best luck at spawns right before sever down, and right after server up when it was a small group trying to avoid the zerg.. Look for signs of people having just left, gold in Despise sometimes winds up in unreachable places, if it's still there it means someone spawned not too long ago. Get Abyss access for you thief, if he's blue (I prefer being blue) take him into the Abyss spawn areas via the abyss sides not the Felucca entrances people seem to find those less of a threat.
Make a regular run through Heartwood, see if anyone is there trying for recipes, or runic fletching tools. This has died off a lot since Imbuing hit, but you can still occasionally find someone after recipes.
Look for places folks will go thinking they are safe to "Roll" for scrolls, guilds with mixed noto don't always run to a house for this, if you can find them you can stalk them.
Check for the PvP Hot spots, Yew Gate on Chessy and Atlantic can yield good rewards, Silver sells ok on a lot of shards, and folks always seem to be toting it around with them, not to mention the odd 110 - 115 scroll. I've even nabbed a few doom arties from folks who went AFK in the gate GZ.
If there is a global event that's happening in Fel, this is GOLD. You'll not only see your normal crew of Reds, but you'll often find a few of what would best be described as "Trammies" trying to dodge the crowds, take advantage of them..
There are few circumstances where you can steal in Tram as well, and it's worth making use of them. If an EM is actively attacking a player while RPing some type of monster, you can steal from the EM if he has anything in his pack. I took a pair of pants, shoes, a shirt, and 1000 gold off an EM playing out the part of Virtuebane in Tram Yew during the funeral of Dawn bit a few weeks back. You might not get anything good but you get to say you robbed an EM.
Listen out for anywhere that known scripters are active in Fel, sure it might not be the same robbing a bot, but killing them and dry looting a full pack of their goodies is always fun and profitable.