In my daily work I am writing a GIS (geographic information system) application.
At my place we work for almost three years with ESRI product, which for a long time lead the market by far, although its critical disadvantages such as: performance problems, poor documentation and expensive price.
but, with no real competitors at sight we could do nothing but pay the greens.

I made some background checking about new GIS Tools mainly because of the performance problems but also because of the unsupervised growing prices.

First I found this great Wikipedia link, which show us all the progress in the GIS domain,
and summarize the known GIS tools. 

I would like to point on my favorite tools:
1) GRASS GIS - free tool for develop your own application, open source, run on MS-Windows, Unix and Mac Os, try this at home.

2) Map Cruzin - enter this site and see what you can do with this one,  couldn't find the API link but friend of mine tell me great stories about writing simple code and this is running extremely fast.

3) GeoTools - this one is my favorite, it has all the features you can only dream about.

I'll keep testing those three deeply throw this year, hope to find the best replacement for ESRI.
I would like to hear another point of view from you, thanks.