http://www.buildtheenterprise.org/Page is very slow (he's working on it, I hope). Just be patient.
According to this guy, supposedly an engineer, it is possible with todays technology. His site explains it all. Gotta love this guy
The Gen1 Enterprise can arrive at Mars within 90 days of leaving earth's orbit. This is derived from various analyses sponsored by NASA that show that with mass to engine power ratios within our reach, a 90 day travel time is possible.