While Visor's USB cradle will work with newer Macintosh models such as the iMac and Power Mac G3/G4, older machines will have to use the serial cradle. A Macintosh adapter is included in serial port cradle package according to a Handspring spokesman. Another alternative would be to buy a PCI card with USB connections. 

What about Linux?

Handspring does not currently have any plans on supporting Linux. As they license 3COM's Palm technology/software, they are dependent on which direction 3COM takes in this matter. There are currently solutions available for synching a serial Palm,  but none for USB connectivity. If you have any info regarding this let us know.