The C(anonical) Scan Matcher (CSM) is a pure C implementation of a very fast variation of ICP using a point-to-line metric optimized for range-finder scan matching.
An incremental laser scan matcher, using Andrea Censi's Canonical Scan Matcher (CSM) implementation.
mrpt_icp_slam_2d contains a wrapper on MRPT's 2D ICP-SLAM algorithms.