As noted on The Total War Community Blog (thanks Frans) now offers a public version of CAS Exporter, Creative Assembly's in-house model and animation exporter for Rome: Total War and Medieval II: Total War. The download can be found on TotalWar.com, where word is: "The CA exporter can be used by modders to export custom created units, siege, props and animations for the Rome: Totalwar engine. It can also be used to export custom strategy map models and unit/siege animations for Medieval2: Totalwar."