A couple that I have on my droid:

Google Sky Map; very cool app for finding or identifying planets, stars and constellations.

GPS status; shows how many satellites your tracking, gives position and time info, other features.

Sundroid; sunrise and sunset times for you location

Moon Phase Pro; moon phase, rise and set times.

Compass; displays a compass using the magnetometer, can also mark waypoints using the GPS.

Droid Light; uses the camera LED flash as a flashlight.

Depending on what model phone you have these may or may not work for you, I find they work very well on my gen 1 Droid.

Have fun.

Regards,

DWS