The Compact Linear Collider (CLIC) project is exploring the possibility of constructing a multi-TeV linear electron-positron collider for high-energy frontier physics studies beyond the LHC era. The CLIC concept is based on high-gradient normal-conducting accelerating structures operating at X-band (12 GHz) frequency. We present the status of development, prototyping and testing of structures for operating at gradients of 100 MV/m and beyond. We report on high-power tests of these structures using the “XBOX” test facilities at CERN and summarize experience with operation at high-gradients. We give an overview of developments for application of the X-band technology to more compact accelerators for use e.g. as X-ray FELs and in medicine.