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 6.2 has been released in two versions by Cisco in February 2015 : "Cisco Packet Tracer Student" and "Cisco Packet Tracer 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 06/11/2015 : Packet Tracer 7.0 is under active development and will include new IoE (Internet Of Everything) features. Last known build is Packet Tracer 7.0 build 106 as of 2015-10-17. No release date has leaked for the moment but active testing activity was reported since july 2015.
Update 17/06/2015: The new Packet Tracer Community forum has been launched a few days ago. This forum is the first one fully dedicated to Cisco Packet Tracer to help users sharing knowledge, labs, bug reports about this application.