I have been a member (MITI) of the Institute of Translation and Interpreting (ITI) since 1998.
Each year since 2003, the ITI has run the Professional Support Group (PSG), a mentoring course for new start-ups in the translation industry. I have served as a tutor on the PSG since since its inception.
I am also a member (MCIoL) of the Chartered Institute of Linguists, a supporting member of the VDSI (Society of German Safety Engineers), and a member of the Stridonium network of professional translators.
Links:
Institute of Translation and Interpreting
ITI Professional Support Group (PSG)
Chartered Institute of Linguists
VDSI
Stridonium