Some online tools allow you to say something to work colleagues anonymously, such as Anonymous Employee or TxtEmNow.com.
The trouble with this sort of anonymity is that it doesn’t allow you to fully resolve a problem.
You may momentarily feel better for having gotten something off your chest. But once you’ve said whatever you want to say, that’s likely the end of it. Your boss will never know who raised the issue, and a co-worker may feel so angry or defensive that he will do nothing to change his behavior.
Rule of thumb: Keep your conversations respectful and results-oriented by “owning” what you say. If you’re afraid to attach your name to it, perhaps it’s better left unsaid.