This great sonar ranger from Devantech offers a wide range from 3cm to 3m. For further range see the SRF08. The SRF04 is interfaced using the one output line to ping the sensor and an input line to read the echo.
This is the SRF05 Ultrasonic ranger made by Devantech. The Ultrasonic detector can detect from ~4 inches to ~13 feet.
This is the SRF08 Ultrasonic ranger made by Devantech. The Ultrasonic detector can detect from ~4 inches to ~30 feet.
These heavy duty gear motors have a rated speed of 44 RPM and a gear reduction of 1:81. These geared motors feature encoders and serve as excellent robot motors, but work great for other uses.
This is a MLT-JR tracked robot platform and is equipped with 32mm motors, a motor controller, and Spektrum remote control. This is a rugged treaded robot platform. The robot handles up to 15lbs of additional payload and travels 300ft/min.