Rob Prior, one of the more talented members of the Traveller mailing list is a Mac programmer. He has a number of useful programs, but Infini-V (known in beta as CSC) is the one that's been voted 'Most Likely To Cause a Gearhead to Buy A Mac'. The shareware ($25 US if I remember correctly) Infini-V implements the design system in IG's Central Supply Catalog sourcebook in an easy to use program. Then you can export the resulting design in any one of a number of native Mac formats or HTML for direct web presentation, as here.
Rob has finished Infini-V, there is supposedly a Windowze version in the works, and he's also said he's working on a similar, more ambitious program to automate FFS2.
We're waiting with bated breath....
I've made a number of vehicles, playing around with Infini-V, and present them here is no grand order...
I've made a series of tanks, a TL3 one, and two TL 4 varieties, one steam powered, the other more conventional