What works and what doesn’t | Practical fact-based SEO Data
If you are looking for SEO/PPC bench mark data to make a case for a SEO budget this guide from MarketingSherpa(this guide has to be bought) will be a useful tool.
Also available (but a little old!) is the guide on Search Engine Optimization as told by 3000+ marketers (the link opens a PDF file) The guide/report was done in 2006 but still has a lot of relevant information for companies just starting out in the SEO space.