Sorry I'm getting a little late to this party, and I missed the synchronous session, but here's my answer all the same!

Question: What’s your experience of using an online reference tool?

Answer:

I suppose it depends on what qualifies as an online reference tool! I've been a long time user of online dictionaries, most specifically Webster's, though more and more I like the flexibility and robust set of results that dictionary.com provides.

In terms of reference tools for teacher development, I think The Sounds of American English by produced by the University of Iowa is a phenomenal resource. (Don't let the name put you off--have a look!)

In terms of recently introduced reference tools, I must say Lextutor looks quite attractive. So much so that I've already mentioned it to several Korean friends who are learning English at the moment. I only wish such a resource existed for other languages!