1) OmegaT is able to translate TTX files that have source=target (output option if I am not mistaken), that requires a small utility called Toxic, to be found here:
http://www.omegat.org/resources/toxic.zip
2) It is possible to deliver "cleaned/uncleaned" file sets by translating the file in OmegaT and processing the resulting TMX in OpenOffice.org with the Anaphraseus macro (a Wordfast equivalent for OOo). The discussion about the process is here:
http://tech.groups.yahoo.com/group/OmegaT/message/14705
And Anaphraseus is here:
http://sourceforge.net/projects/anaphraseus/
(updated 7/8)
3) Ask your Trados clients to send you TMX memories instead of Trados memories, you'll be able to use them in OmegaT without problems. Trados seems to have problems creating conforming TMX files. If OmegaT complains, use TMXValidator from Maxprograms.
TMXValidator is here: http://www.maxprograms.com/products/tmxvalidator.html
4) Some file formats are not directly supported by OmegaT. Use Rainbow to create OmegaT projects from unsupported files. Not all files supported by Trados are supported by Rainbow but Rainbow still covers a very reasonable range of "exotic" formats.
OmegaT directly supports the following formats:
- OpenDocument/OpenOffice.org
- Microsoft Open XML
- DocBook XML
- HTML, XHTML
- TeX
- Plain text
- SRT subtitles
- PO (monolingual)
- XLIFF (Okapi generated)
- ResX ressources
- INI ('key=value' format)
- Java bundle.properties
- HTML Help Compiler
- QuarkXPress CopyFlow Gold