Velvet is a de novo assembler intended for next generation reads. Velvet is ideal for assembling Illumina sequencing reads of bacterial genomes on a mid range Mac. With paired read data it produces very good contigs. For example a 7Mb genome with an N50 of 103kbp was produced from 16 million paired Illumina reads in one hour on a 16GB 2007 Mac Pro.
For more details on using Velvet see the Velvet technical page