Selling with standard assets.

Can you sell games that use the standard assets, and terrains made with the terrain assets?

Yup. Actually, the terrain asset license is on the front page of the download site:

All assets including models, textures, sounds and scripts are available for free commercial and non-commercial use when used in a Unity game.

See HiggyB's reply in this thread -

http://forum.unity3d.com/viewtopic.php?p=215667&highlight=unity+assets#215667