Lenmar standard battery for Dell Streak available for $24 or less
You may remember Lenmar as the company who makes the Universal Clip Charger that can be used to charge a Dell Streak battery outside of the device. That product isn't marketed for use with the Streak, but here's one that is.
It's a 1530mAh li-ion battery—the same capacity as the standard Streak battery that Dell sells for $40—and it can be yours for a penny shy of $24 (MSRP). That's more expensive than a generic $10 battery, sure, but the item comes for a fairly well known company and is still cheaper than the official OEM battery.
Lenmar doesn't sell it directly, but you can get this battery online at Best Buy for the list price and Thomas Distributing (I've never heard of them) for an even more affordable $18.
[Lenmar]