This week's online find (thanks to a facebook group of music teachers I'm part of) has been this wonderful online xylophone through Playsprout.
It's a simple diatonic xylophone (one octave, in C) but has really good response times and works well on both iOS devices and laptops (my students are using a mix of ipads, netbooks and chromebooks depending on year level, so finding something that works across multiple platforms is great!)
If using a laptop, there are a number of keyboard shortcuts which make for really quick and easy playing and any touch-screen devices mean you're able to play it just like a real xylophone (well, perhaps without the mallets!)
This online xylo is great for short sing & plays, for students to record compositions on, or to work out known songs using absolute pitch names.
It's also capable of playing multiple notes at once, so this is great reinforcement for my older students looking at chords and harmony!
The online xylophone can be found here