Free and open source

An object detection function in ImageJ. [Analyze > Analyze Particles...]. It could simply be used for counting number of cells, but could also do more complex stuffs. ## Jython Snippet Here is a snippet of how to use Particle Analysis in Jython script.

ImageJ macro for the morphometry of neurites. > NeurphologyJ; it is capable of automatically quantifying neuronal morphology such as soma number and size, neurite length, neurite ending points and attachment points. NeurphologyJ is implemented as a plugin to ImageJ, an open-source Java-based image-processing and analysis platform.

Estimate the frequency of hepatitis C virus infected cells based on the intensity of viral antigen associated immunofluorescence. 

The core is an ImageJ Macro, so it's easy to modify for one's own needs (Link to the code). 

XuvTools (pronounced “ex-you-vee-tools”) is a fully automated 3D stitching software for biomedical image data, typically confocal microscopy images. XuvTools runs on Microsoft Windows XP and Vista, Linux and Apple Mac computers. It supports 32 and 64bit operating systems (with 64bit highly preferred). XuvTools is free and open source software (see Licensing), so you can start using it immediately. Go to Downloads and give it a try. The goal of XuvTools is to provide tools, that combine multiple microscopic recordings to obtain a larger field of view (“stitching”) and a higher dynamic range (“HDR” recombination), or better resolution (multi view reconstruction), and to make these tools publicly available.