Alchemically Organized Music (A.O.M.) has released an updated version of Invisible Limiter - a freeware brickwall limiter.
Here's what they have to say about Invisible Limiter:
The Invisible Limiter is a transparent look-ahead brickwall limiter with automatic attack/release-time optimization. The Invisible Limiter's limiting algorithm minimizes the difference between the original and the limited materials.
Pricing and Availability
Invisible Limiter is available now as a free download.