Considering the only real options are USB and Firewire, if you have a USB port and no Firewire, you've chosen the only option available to you. Firewire is a preferred connection for speed and CPU utilization, but USB is more widely compatible if you needed to plug the drive into more than one machine.
If you had an external SATA port, you could get a laptop drive with SATA connectors and an external enclosure supporting eSATA, but I'm assuming you have an existing drive with IDE connector.
If you're looking for specific brands, look through other threads as this sort of thing gets asked a lot, and you can look for other site reviews. Generally even the cheap model enclosures will work well enough.