Enjoy!
1. Smashing Named Enemies
Roo Morgg used to be a great spot to collect rares and sell them later. You can still do that, although it will take a lot more time. The developers have drastically changed the chance of getting rares from Roo Morgg, making it much harder. The spot is still excellent for gathering coins dropped by Roo Morgg. The ape usually drops between 400-500 coins per smash, and this can really add up over a while.
2. Smashing Stromling Apes
Stromling Apes are currently only found in the Gnarled Forest, although with the release of Crux Prime tomorrow (YAY!) you can also find more powerful versions of them there. By just quick building the anchor that lies near them, you can gain up to 300 coins per ape. This also leads to a series of achievements that can eventually get you the ultimate weapon in Lego Universe. The Elite Force Blade Of Lightning!
3. Selling/Trading rare items
If you have found a rare item that you don't think you need, or maybe even an elite weapon, you can get other people to pay a way over the top price for it. There have been elites that were sold for over 15,000 coins. Also, items like the santa beard and the king's crown, have gone for 25,000. So if you are the lucky type of person who can get lots of rare items but doesn't really need them, try selling them to somebody else who take it.