Since this is not for synthesis but for reversing, ALL cell libraries, regardless of cost, are important. This page aims to be a complete collection of all cell libraries that might be encountered during analysis.
Previously Artisan Sage
Free, but no longer available.
Use to have the Crete library, but it seems it fell off of the ends of the earth. Some info about it can be found here:
FOSS, resembles BSD style licensing
All created with Alliance software.
These do not provide libaries themselves, but many links here were taken from them and may get updated before this page
Open source collection