In the following namespace: System.ComponentModel.DataAnnotations, there are the following annotations available:

KeyAttribute

StringLengthAttribute

MaxLengthAttribute

ConcurrencyCheckAttribute

RequiredAttribute

TimestampAttribute

ComplexTypeAttribute

ColumnAttribute

Placed on a property to specify the column name, ordinal

TableAttribute

Placed on a class to specify the table name and schema

InversePropertyAttribute

Placed on a navigation property to specify the property that represents the other end of a relationship

ForeignKeyAttribute

Placed on a navigation property to specify the property that represents the foreign key of the relationship

DatabaseGeneratedAttribute

Placed on a property to specify how the database generates a value for the property (Identity, Computed or None)

NotMappedAttribut

Placed on a property or class to exclude it from the database

It's nice to know that using this attributes is allso influences the database.
A field with a MaxLentAttribute will become a nvarchar max field.
A field with a MaxLentAttribute wich specifies 4 will become a nvarchar(4) field in the database.

Entity object attributes

Next to data anotations for the properties of the Entity Object class there are a few attributes available for the Entity Object

Serialize atrribute

If you need to serialize the Entity object it needs to be decorated with the Serialize attributed.

DataContractAttribute 

If yo want to pass the Entiry object through a WCF service you entity object needs to be decorated with the DataContractAttribute