This is an implementation of a subset of roundup(1) in Go.
For the original utility (that is considered to be the mainline) go to https://github.com/bmizerany/roundup

A good introduction is here: http://itsbonus.heroku.com/p/2010-11-01-roundup

The main motivation for this particular implementation was speed. Benchmarks:

(original roundup):
time sh ~/roundup/roundup.sh all-test.sh
...
Tests: 1355 | Passed: 1355 | Failed: 0

real 1m8.612s
user 0m0.110s
sys 0m0.480s


(Go roundup):
time roundup all-test.sh
...
Tests: 1355 | Passed: 1355 | Failed:   0 |

real   0m42.342s
user   0m0.570s
sys    0m0.740s

(Go roundup with -j2):
time roundup -j2 all-test.sh
...
Tests: 1355 | Passed: 1355 | Failed:   0 |

real   0m16.752s
user   0m0.400s
sys    0m0.530s

(Go roundup with -j8):
time roundup -j8 all-test.sh
...
Tests: 1355 | Passed: 1355 | Failed:   0 |

real   0m6.071s
user   0m0.520s
sys    0m0.750s

6 sec vs 68 sec is a big win for me.