IronPython is an open-source implementation of the Python programming language which is tightly integrated with the .NET Framework
IronRuby is an open-source implementation of the Ruby programming language which is tightly integrated with the .NET Framework.
"Also i believe the ironruby team is smaller than the ironpython team"
from question "Why doesn't IronRuby have the same tools that IronPython does?"
"However as things stand right now ironpython is much more mature and has much better performance than ironruby so you may prefer to use that"
from question "Extending C# .NET application - build a custom scripting language or not?"
"Ironpython has had more time to focus on performance improvements but ironruby has made significant performance improvements as of late"
from question "Performance comparison between IronRuby and IronPython"