[vimalbhalodia]

I personally think MakeBlock (http://www.makeblock.com/) does a great job of being a modernized metricized replacement for Erector sets.

It's not particularly cheap - probably costs ~$300 to get a decent sized kit or a smaller kit with enough spare parts to experiment.

All of the mechanical parts are machined reasonably well and fit together in a large number of useful configurations - I really like them for rapid mechanical prototyping.

The electronics are basically arduinos with beginner-friendly connectors - haven't used them myself but have generally heard good things about them.