Are there any programming languages where the system parallelizes the program without any noticeable differences for the programmer?
That is, the programmer writes a linear, deterministic program, without any additional tags or meta-data, and the underlying system parallelizes all of the work.
haskell has a host of parallelism and concurrency features. STM has been popularized and much-discussed since being implemented by haskell. you might also like Go, it has a channel feature that may be of interest.