Recs.
Updated
Pharo is an innovative, open, integrated and highly productive eco-system comprising language (forked from Squeak Smalltalk), modern libraries (extensive), very rich and integrated IDE, meta programming tools, cross platform virtual machine(s) and a small but growing and thriving community including academics and industry partners. Now at Release 5 (stable, March 2016) with Release 6 well under way in development community.
Pharo can be used for server and client programming. It is open with easily used networking, parsing, generating and persistence frameworks.
SpecsUpdate
Pros
Pro Glamorous toolkit & GTInspector
Most languages are still copying the Smalltalk tools of yesterday - GTInspector (written in Glamorous) takes live exploration of code/running objects to a new level. It's really slick, and better yet, you can easily write your own inspectors in 10 lines of code.