A good source for information are the Workshops on SRF technology. The most recent ones are available on the WWW:
SRF1999,
SRF2001,
SRF2003,
SRF2005,
SRF2007.
Another source are specialized Workshops on SRF technology.
2004 Argonne, USA : "Pushing the Limits of RF Superconductivity"
2006 Araxa, Bresil: "Single Crystal Niobium Technology Workshop "
Lectures
The SRF workshops have intorduced lectures for new students:
2005 lectures
2007 lectures
The ILC Accelerator Schools also offer lectures on SRF and related topics:
2006 lectures
2007 lectures
2008 lectures
Particle Accelerator Conferences
Several series of conferences deal with particle accelerators. On nearly every conference material about SRF technology can be found. A good source of informations (esp. papers) is the 'Joint Accelerator Conferences Website' (JACoW). In the near future the SRF Workshop Proceedings will be included in the Jacow database.
Collaboration Meetings
The meetings of the TESLA collaboration are also a source for information about superconducting RF technology e.g. the TESLA Technical Design report (TESLA TDR) .