Yes, but CHDK is the best-known example and there do not seem to be similarly established options across all brands. From the answers here, CHDK is the only widely recognized project of that type. There are also community efforts focused on analyzing or decrypting firmware for some Pentax DSLRs and for several Nikon models, with Nikon hack development reported for cameras such as the D7000, D3100, D5100, V1, and J1. That said, these projects are not presented as broad, CHDK-style solutions for every brand. Based on the information provided, there is no confirmed equivalent for HP cameras.