Cisco Packet Tracer is a powerful network simulator that can be utilized in training for CCNA TM and CCNP TM certification exam by allowing students to create networks with an almost unlimited number of devices and to experience troubleshooting without having to buy real CiscoTM routers or switches.
Cisco Packet Tracer features an array of simulated Application layer protocols (HTTP, DNS, …), as well as basic routing with RIP, OSPF, and EIGRP, to the extent required by the current CCNA TM curriculum. It also includes Cisco IOS 15 with licence features which was introduced in the CCNA exam in 2013.
Cisco Packet Tracer 6.3 has been released on 22th december 2015 by Cisco. This is a maintenance version with netacad login enabled at application startup. It replaces Cisco Packet Tracer 6.2 Student and Cisco Packet Tracer 6.2 Instructor. Cisco Packet Tracer 6.2 includes an ASA 5505 firewall with command line configuration (but no Adaptive Security Device Manageror CCP tools). It also includes a netflow collector as a Desktop application in the server device, routing protocols for IPv6 (OSPFv3, EIGRPv6 , RIPNg), DHCP snooping commands, IPv6 CEF, IPSEC ...
Packet Tracer 6.2 introduced 3G/4G telephony support as well as a new Cisco 819 ISR router with a embedded wireless Access Point. OSPF and EIGRP enhancements were also added in this new version.
Update 06/03/2016 : Packet Tracer 7.0 is under active development and will include new IoE (Internet Of Everything) features and a new Cisco 2100 wireless lan controller (WLC). Last known build is Packet Tracer 7.0 build 116+ as of 2015-11-22. Packet Tracer 7.0 is expected to be released on 29 July 2016 as Cisco announced it last week on it's website.
Update 01/05/2016 : Prepare the CCNA and CCNP datacenter exam using UCS server emulator (UCS PE) and VIRL NXOS simulator. Thse two tools will help you get strong practical experience on the Cisco main datacenter technologies before taking the exam. Enjoy ;-)