All students are encouraged to own their metronome, but for those times when one is not readily available, try one of these:
New advanced metronome - simulates Dr. Beat and allows you to create your own combinations of beats/time signatures. Very cool.
Metronome online - this is a replica of the classic dial-face metronome and sounds like one, too.
WebMetronome - a different style of metronome that allows the user to select various beats for accentuation. Great for 5/8 and 7/8 Includes a practice timer!
Bouncing ball metronome - this is very basic and may not even keep an accurate tempo, but gives the user a visual aid to help them track the beat.