There's the super-duper accurate Microinfinity gyro with a 1 degree per hour drift rate (that is really, really low) and can also calculate your current heading and a few other things. This sensor is digital.
And the slightly less accurate but cheaper HiTechnic gryo sensor. This sensor is analogue.
HiTechnic also make a really good colour sensor that can detect a preset of 17 colours but also does raw RGB and a few other modes.
As for the battery charger and battery, I use both the standard LEGO battery pack and rechargable NiMH 2750 mAH AA batteries. I couldn't really give you an address of where to get them because that depends on the country/continent you live on
- Xander