HTC HD2
iPhone 3GS - iOS4 (multitasking)
Google Nexus One.
Samsung Galaxy S (soon-releasing)
Motorola Droid X

At the moment i will be looking at these phones, besides the moto and samy because they are just new to market and could be bought only on contracts, but the rest are solid good phones that have been on the market for a while, and can be purchased unlocked for reasonable prices.