GaussFit OnSpot

quote: 

GaussFit_OnSpot is an ImageJ plugin for fitting Gaussian profiles onto selected positions in diffraction-limited images (e.g. single molecules, protein clusters, vesicles, or stars).

The plugin performs a function fit in regions of interest (ROI) around spots marked by point selections in grayscale images. Single or multiple spots can be either selected manually with the Multi-point tool or automatically with the Find Maxima function.

There is a PDF with more information, and also an example image.