List of free rfc3161 servers.

rfc3161.txt

http://sha256timestamp.ws.symantec.com/sha256/timestamp
http://timestamp.globalsign.com/scripts/timstamp.dll
https://timestamp.geotrust.com/tsa
http://timestamp.verisign.com/scripts/timstamp.dll 
http://timestamp.comodoca.com/rfc3161
http://timestamp.wosign.com
http://tsa.startssl.com/rfc3161
http://time.certum.pl
http://timestamp.digicert.com
https://freetsa.org
http://dse200.ncipher.com/TSS/HttpTspServer
http://tsa.safecreative.org
http://zeitstempel.dfn.de
https://ca.signfiles.com/tsa/get.aspx
http://services.globaltrustfinder.com/adss/tsa
https://tsp.iaik.tugraz.at/tsp/TspRequest
http://timestamp.apple.com/ts01