Google+ Games

These games are free to play.

City of Wonder: Start from newly sedentary, and grow your population. Allies are required to build some buildings. Gold is little and slow to earn if you don't want to spend money; it is needed to unlock certain tech tree items and purchase buildings. The Ally bonuses and free gifts look to be quite useful, too.

Edgeworld: An isometric tower defense where you are in control of a base, its operations, and the attacking of other bases, such as another player's, or an NPC's. Platinum must be purchased with money, as far as I know.

Flood-It!: It's a game of color subtraction. There are six color values: Magenta, Blue, Yellow, Red, Cyan, and Green. The boards are generated randomly. You only have twenty-five moves to make all of the pixels a single color. Expect to lose more than you win. No premium content here.

More information on the games listed...

City of Wonder: There is no public chat channel.

At level 10, you can place a marketplace, and at level 12, you can place a workshop.

By the way, with enough player allies, boundaries can be expanded at the cost of silver instead of gold.

Edgeworld: There are four chat channels. They are local, alliance (/a), group (/g), and world (/w).

Upgrading the base takes forever, and is worth it.

Commander levels are quick to gain. Each level is +10% attack power and health (units and buildings). The first twenty or so levels are quickly earned by completing a number of quests

The queues are building (constructing and upgrading the base's buildings), research (unlocking units, and increasing unit levels), training (barracks units), assembly (mechanized units).

Flood-It!: Apparently, there's an app for that... It's free, too. Not to mention a bit more challenging, so says my sister. (Paraphrased, of course. )