G1 USB Host
From Android Wiki
According to sources close to HTC, the msm7k chip in the HTC Dream (Aka G1) has USB host capabilities.
The official kernel provided for these phones definitely does not have any USB host capabilities enabled, and on the kernel tree available for the htc_dream, there is not anything to enable it.
In order to enable USB host, documentation from Qualcomm will likely be required.
Information read 2009-08-04 on the net. When the USB cable is connected and the SD card installed, one can click on the USB logo in the notification bar and select mount. Now the Android works as a removable disk. Unmount before disconnecting the cable.