Via plt-dev:
I’m pleased to announce the initial release of parallel futures, a construct for fine-grained parallelism in PLT. Roughly speaking, a programmer passes a thunk to ‘future’ and it gets run in parallel. That “roughly” holds a few gotchas, partly because we’re just getting started and partly due to the technique we’re using. See the documentation for more details:
http://pre.plt-scheme.org/docs/html/futures/