As part of my research, I have developed a toolkit in C# for training and testing CRF models. This toolkit runs on .Net in a windows environment, as well as under Mono on Linux.
The toolkit incorporates a variety of feature functions (transitions, spline feature functions, moments, skipe edges etc.), and is flexible in that the feature functions to be used in a particular model may be specified arbitrarily for a given dataset.
I am in the process of packaging a version of this toolkit to make available online. However, this process may be expediated somewhat if some interest is shown in using this CRF implementation.
Please email me at mss46 AT cam ac uk if you are interested in obtaining a version of this toolkit.