Glassdoor is okay for the UK at least, I use it to check the Software Developer and Solutions Architecture average wages nearby to were I live. The amount of data seems to be getting worse lately though, wonder if certain companies are asking for data to be removed.
Glassdoor's website states "Your trust is our top concern, so companies can't alter or remove reviews." so at least the reviews are genuine but of course, that does not mean some other data (salaries) are not being altered.
