If i had an n900 in my hands, i would use the "mode" sysfs node of the musb driver, valid parameters are "host", "peripheral" and "otg". I'd switch it to the host mode and measured with DMM if there's power on the Vbus and checked the resistance between DM/DP and GND (should be ~15k). I'd connect what's lacking externally and tried attaching some mass-storage device or a mouse.