Runescape
Tribal Wars
Evony
References :

1) You can trade them in the marketplace with other players. The offers depend entirely on the generosity of other players as well as the stage of the game you are in. In the beginning crop is plentiful and clay is scarce. By end game however crop is in high demand and some players will give you as much as 2:1 iron/wood/clay for crop.

2) You can use the NPC calculator in your marketplace. Although it costs you 3 gold to use, you’ll be trading on a 1:1 basis with the "computer", which means you can do these trades at any time.

As for what you’re planning on building at the outset, I’d recommend reading a guide to help you along, especially if you’re getting somewhat addicted to the game. Probably the two best ones out there are:

"Travian on Crack" – http://www.travianoncrack.com – (beginning of the game)

and

"Tips 4 Travian" – http://www.tips4travian.com/ – (offensive, growth, and defensive strategies for the game)

Good luck!
References :
http://www.travianoncrack.com
http://www.tips4travian.com

Kingdom of Loathing: http://www6.kingdomofloathing.com
Free, hilarious game. The artwork is stick figures, but since the whole game is very tongue in cheek, it’s very fitting. Unfortunately you only get a certain number of turns per day.

Fallen Sword: http://www.fallensword.com/?ref=112924
More like your classic RPGs, but again only a certain number of turns per day. Great community there though.

Anyway, I hope these are helpful for you!
References :

On the doubloon oceans ("servers", as ye landlubbers call ‘em), you can play for free. The game has two kinds of currency, doubloons and pieces of eight, and many items and services require you to pay a little of both. Pieces of eight can be earned in all the quests, wagering games, etc., but there are only two ways to get doubloons: buy them with real money, or trade pieces of eight for them on the in-game market.

What that means is if you have enough pieces of eight–from running a successful shop, winning at poker, or just grinding away for hours–then you can get access to all the features of the game for free. If not, then you have the option to buy doubloons, or you can just forego the advanced features. You can still play without spending a single doubloon on anything, although you won’t be able to play as a captain or officer, won’t be able to play the parlor minigames except on the days when they’re free to everyone, won’t be able to buy land or expensive swords and clothing, and so on.
References :

Here’s a description of Anarchy Online from their site:

Anarchy Online is the Ultimate Sci-Fi based Massively Multiplayer Online Role Playing Game (MMORPG)
Play with tens of thousands of other gamers online in a massive virtual world on the planet of Rubi-Ka
Create and customise your own character, choosing from fourteen diverse professions. Be a Soldier, Doctor, Engineer or many more, the choice is yours!
Utilise our ground breaking auto-generated content system to enjoy personalised mission dungeons tailored to your level and location!
Experience the fast and exciting Player versus Player Action
Develop your character with thousands of items of armour, weapons and other upgrades!
References :
http://anarchyonline.com/