Estou tentando fazer um teste com jpa hibernate e oracle 11g

<persistence-unit name="contas-oracle">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <class>br.com.caelum.financas.modelo.Conta</class>
        <properties>
               <property name="javax.persistence.jdbc.driver" value="oracle.jdbc.OracleDriver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:oracle:thin:@localhost:1521:CONTAS" />
            <property name="javax.persistence.jdbc.user" value="system" />
            <property name="javax.persistence.jdbc.password" value="system" />

            <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle11gDialect" />
            <property name="hibernate.hbm2ddl.auto" value="update" />
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="true" />   
              <property name="hibernate.hbm2ddl.auto" value="create" />
           </properties>

porém da esse erro.

no console

Set 13, 2014 1:59:25 PM org.hibernate.annotations.common.Version <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {4.0.1.Final}
Set 13, 2014 1:59:25 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {4.1.9.Final}
Set 13, 2014 1:59:25 PM org.hibernate.cfg.Environment <clinit>
INFO: HHH000206: hibernate.properties not found
Set 13, 2014 1:59:25 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
Set 13, 2014 1:59:26 PM org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
INFO: HHH000402: Using Hibernate built-in connection pool (not for production use!)
Exception in thread "main" javax.persistence.PersistenceException: [PersistenceUnit: contas-oracle] Unable to build EntityManagerFactory
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:915)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:890)
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:57)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:63)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47)
    at br.com.caelum.financas.jpa.TesteJPA.main(TesteJPA.java:46)
Caused by: org.hibernate.service.classloading.spi.ClassLoadingException: Specified JDBC Driver oracle.jdbc.OracleDriver class not found
    at org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl.configure(DriverManagerConnectionProviderImpl.java:107)
    at org.hibernate.service.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:75)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:159)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:131)
    at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.buildJdbcConnectionAccess(JdbcServicesImpl.java:223)
    at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:89)
    at org.hibernate.service.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:75)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:159)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:131)
    at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:77)
    at org.hibernate.cfg.Configuration.buildSettingsInternal(Configuration.java:2283)
    at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:2279)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1748)
    at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:94)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:905)
    ... 5 more
Caused by: org.hibernate.service.classloading.spi.ClassLoadingException: Unable to load class [oracle.jdbc.OracleDriver]
    at org.hibernate.service.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:141)
    at org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl.configure(DriverManagerConnectionProviderImpl.java:104)
    ... 19 more
Caused by: java.lang.ClassNotFoundException: Could not load requested class : oracle.jdbc.OracleDriver
    at org.hibernate.service.classloading.internal.ClassLoaderServiceImpl$1.findClass(ClassLoaderServiceImpl.java:99)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at org.hibernate.service.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:138)
    ... 20 more