Hi,
In Hanoi, you can rent motobike on Old Quater to visit Ba Vi national park, Tam Dao, or some outside of Hanoi such as Duong Lam acient village, Bat Trang village, Van Phuc silk village where you can transfer by puplic bus.
In HCMC, you can visit Mekong Delta. Vung Tau beach.
Check out: http://www.vietnamtourbooking.com