The goal of Xplico is extract from an internet traffic capture the applications data contained.
For example, from a pcap file Xplico extracts each email (POP, IMAP, and SMTP protocols), all HTTP contents, each VoIP call (SIP), FTP, TFTP, and so on. Xplico isn’t a network protocol analyzer. Xplico is an open source Network Forensic Analysis Tool (NFAT).
Xplico is released under the GNU General Public License and with some scripts under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0) License. For more details see License.
Features

Protocols supported: HTTP, SIP, IMAP, POP, SMTP, TCP, UDP, IPv6, …;
Port Independent Protocol Identification (PIPI) for each application protocol;
Multithreading;
Output data and information in SQLite database or Mysql database and/or files;
At each data reassembled by Xplico is associated a XML file that uniquely identifies the flows and the pcap containing the data reassembled;
Realtime elaboration (depends on the number of flows, the types of protocols and by the performance of computer -RAM, CPU, HD access time, …-);
TCP reassembly with ACK verification for any packet or soft ACK verification;
Reverse DNS lookup from DNS packages contained in the inputs files (pcap), not from external DNS server;
No size limit on data entry or the number of files entrance (the only limit is HD size);
IPv4 and IPv6 support;
Modularity. Each Xplico component is modular. The input interface, the protocol decoder (Dissector) and the output interface (dispatcher) are all modules;
The ability to easily create any kind of dispatcher with which to organize the data extracted in the most appropriate and useful to you;

the site says it can install and free to use in any linux distro

download:

http://www.xplico.org/download