Information about standard cells can be difficult to find. None of the commercial companies (Artisan, Virage etc) publish data books and certainly don't publish their layouts. So claims like "provides up to a 30 percent increase in utilization when compared to conventional standard cell libraries" have to be taken on trust.

I have tried to gather publicly available information on standard cell libraries on the following web pages. Not all of these libraries are open source, so check the licence restrictions. Some libraries are not really available for design work, but they can provide useful ideas.

The libraries which are really available and can be used for design work are the ones on this web site, the MOSIS Tanner ones, the Alliance sxlib and the IIT/OSU libraries. The other libraries either no longer can be found on the web, or are incomplete, or a registration form has to be submitted like a commercial library.

There is also a web page with a comparison of gate densities for various open-source and commercial standard cell libraries.