I've been meaning to release a "standard" cucumber-in-parallel cross-browser project for awhile now, but I just got around to it this weekend. It's called Cucumber Sauce.
Run your cucumber tests across different browsers all at the same time
Browsers are configurable via a yaml file
Multiple browser config files are easy to setup, and one can be passed in when running the rake task. Have a browsers_core.yml file to run while developing, and a browsers_full.yml to run before pushing to production
Designed to run tests ultra-cleanly. Adds time overhead initially, but tests are all independent of one another, and can be made to run in parallel at the scenario level in the future. Follow this template or you'll lose that ability to speed up your tests.
Check it out at the Cucumber Sauce github repo.