Recently more vendors such as Sparkling Logic and Signavio announced that their tools now support the DMN standard. They joined the initial DMN implementations provided by OpenRules, Sapiens, and a few others. Nick Broom, a well-known DM practitioner and a contributor to the DMCommunity, provided his review of the Signavio implementation, and promised to provide a review of the FICO DMN Modeler that according to Alan Fish is coming next month – see this LinkedIn post.
We plan to prepare a complete list of the current BR&DM vendors who support the DMN standard. This list along with reviews from practitioners will be published and maintained at this website. If you are a vendor and want to be included into this list, please update your profile at the Live Catalogs of BR and DM tools and email us a link to your implementation.
dmcommunity.org 
On May 9, 2015 JBoss Drools announced that they are also “working towards Decision Model and Notation support, that allows networked diagrams of Decision Tables” http://goo.gl/EfJ8zg
DecisionsFirst Modeler (http://decisionsfirst.com) is a DMN-focused decision modeling tool that’s been commercially available for a while, that has a free version for up to three users and that is available both SaaS and on premise.