Search for Stephan Grossman he produces a Book/ CD and corresponding DVD for beginning bottleneck blues playing. You can probably find YouTube samples. A faster pace would be the 3 DVD set from Bob Brozman.
Check out Keni Lee Burges at firstname.lastname@example.org he has a lot of instructional material and they are all only $9.99. I had one of his 4 string Cigar Box videos and it was great. Check this out, He is also a respected member here http://www.cigarboxnation.com/ and it's fee to join. I believe it is approaching 4-5,000 members. Good luck.
I forgot about Keni Lee's YT videos, didn't know he had lessons for sale, thanks Grizz, I'll check them out myself. I also forgot one of my favourite slide guys, Steve James, he's got a DVD out as well, but not strictly slide.
not a lot out there on this subject. I am interested myself. I ran a google search for " bottle neck blues " lessons and I got a few websites. nothing great enough that I think it needs sharing. best you run the search for yourself and make your own judgement. I found a nice app for my iPad called "slide guitar" it had some tab and then jam tracks to play with. It shows open e, g, and d stuff. 3 songs for each tuning. may not be complete songs though, there isnt enough measures to be a complete song. it's maybe 3 days of learning if you are slow like me. the jam tracks are ok. a person can play about anything over a jam track as long as you are in the right chord.