My exposure to software and SaaS is a patchwork, built from varied experience:
KLD - SaaS sales for socially responsible investment research professionals: B2B
Lightservers - free and open source software tools for individuals: B2C
Grass Commons - open source product futures built for individuals to understand the implications of their purchases
E Source - Most of the work I did here was research, but the most interesting aspect was the ETDB: the emerging technologies database. This is where WagN came back into the picture -- my colleague and I used it to put together a web-based platform to build the ETDB, a database to help utilities better understand and communicate about emerging energy efficient technologies from lighting to HVAC to pumps and control systems.
PONT380 - SaaS and proprietary analytical tools to help corporates improve their renewable energy strategies and structure internal investments in energy efficiency 'protfolios,' opportunities to invest in energy efficiency measures that have better return profiles than a firm's internal hurdle rate with virtually no risk.