Being in magic almost 20 years, I have been to many lectures / workshops taught by many magicians as we watched on videos / DVDs/ instant download as technology progress. Many of them still with us, some were gone, and if ask who is the best is definitely a tough question to answer since everyone have their own favorite.
However, I can narrow down to three I personally believe that I benefit most from, in no particular order:
1. Tom Stone - I fortunate enough to attend his special one day workshop last year, he made me realize that everyone can be creative no matter how we think we do not, I owe him a big thank you for that.
2. David Williamson - one of the two magicians on this planet I will take a flight to meet him whenever possible. He might explain the same effect in the lecture however every time you watch and listen you just learn something more every time. Who can argue that even Tony Chang attend his lecture just because for his tips on DPS?
3. Juan Tamariz - For those who believe, no explanation is necessary... Juan is the best close up magician we have in our era after Dai Vernon, period. The first time saw his close up salon a decade ago made my eyes 'opened' and redefine what magic is. Juan's lectures, workshop, publications whatever available I started to read and digest into my brain ever since. I fortunate to attend his workshop twice. Currently Juan has small class each year for an extremely limited quota (7-10 students) each year for people to apply and study at his home for 3-5 days straight, price is not cheap, but I look forward some time in future my schedule is available to meet him again personally.