"The Green Monster"
David Rieben's GM is a 12" ARSG coil
This to my mind is a mini version of the BIGGG one (shown above). Its large toroid (54" I think) is part of the key to its excellent performance. A truly impressive coil.
These coils all produce nice thick streamers: raw power at its very best.
The above coils are all of the conventional (or 'classic') type using a spark gap, which means that no solid state electrics are used in their construction - much easier and cheaper, but without the capability to play a musical tune. Personally I can live without the musical coils, just show me a good solid white hot streamer anytime!
There are lots of websites covering Tesla coils, and below are a few that I have found to be a cut above the rest. Because of the knowledge that these people have on the subject they are a very good starting point to learn about Tesla coils.
A good newsgroup for Tesla coils is the Tesla Coil Mailing List. Apart from posting queries, there is also plenty of information for spark gap coils in the archives, which are both extensive and searchable.
A very comprehensive site with good theory from a man who really knows his subject is Richie's Tesla Coil Webpage.
Another comprehensive site is Terry's Tesla Coil Site.
Bart Anderson's excellent software (JAVATC) for designing Tesla Coils at Classic Tesla
Both electronic and conventional coils here, along with reports from all the UK Teslathons (or 'Gaussfests' as this site calls them) Extreme Electronics
Useful Java tools, plus a step by step guide can be found at: Deep Fried Neon.
A good collection of various sites was found at the Hot Streamer site. (Now closed but the archives are to be found at that link.)
Another nice site worth a visit is Hazardous Physics with some informative content and good photographs covering the construction of two different tesla coils. Also covers construction of a Gauss cannon (coilgun).