The Frontier self-adaptive versatile limiter, produced by D16 Group, is an outstanding plugin that's freely available to anyone registered D16 users.
If you are in need of a limiter for either mixing or mastering, I might have found the one for you! This plugin is a beast. It can go from gentle, transparent, gluing of a mix, to full blown saturation. Best of all, it's FREE!
One of my favourite functions is the soft clip switch which gives an incredibly nice saturation to the sound, the knobs are labelled clearly, with the black bars denoting the extreme settings where things get really fun.
A handy feature is the auto gain normalisation where after compression it brings the level back up, which of course, you can then change.
The release is a simple three option switch, great for ease of use, but important enough to be there. I recommend for mastering using two of this plugin in series, one with a fast release, and one with a slow one.
Since playing around with it for a few weeks now, I can happily say this is the limiter for me. It's use as a creative tool is important too, especially for the nice saturation, which in my opinion, beats many free saturator plugins.
If like me, you are stuck using an under-powered computer for most things, then you can still use this with ease as it does offer quality settings to reduce the CPU load. Especially when you are using two of these plugins in series for transparency the load can become significant.
I do highly recommend you bump up the quality before rendering however as there is a noticeable difference between the quality settings. For monitoring though, the low settings will do just fine.
For some more general tips on compression, check out:
How To Avoid Losing Character With Compression
What Does a Compressor Actually Do to the Mix?
How to Make your Mix Louder