Just thought I would share this deal I found on eBay for replacement batteries!
It comes with 2 1500mah (200 more than OEM battery) and a Battery Cradle style Charger so you can charge one out of the phone, and just swap them out when you need to

I am going to order a set and will let everyone know how the performance stacks up.. even if it only gets an extra hour or 2 per charge, $17 bucks for 2 of them, AND a charger, can't beat that deal

link:
http://cgi.ebay.com/2x-BATTERY-DESKTOP-CHARGER-FOR-VERIZON-HTC-DROID-ERIS_W0QQitemZ270519582451QQcmdZViewItemQQptZPDA_Accessories?hash=item3efc393ef3#ht_2273wt_802Update:
I just ordered them, but realized they are coming from Hong Kong, so it may be a week and a half to 2 weeks before I receive them, But I will be sure to let everyone know how they work out when i get them!
tried the link but it says "This listing (270519582451) has been removed, or this item is not available" is there a different link for the batteries??