If I had to pick just one, surf/instro is probably my favorite musical genre. And like most music categories, it has it's sub-genres (horror surf, spy surf, surfabilly, etc). Fortunately, even the stuff that falls into the sub-genres still sounds fundamentally "surfy" and doesn't stray too far from it's distinctive sound.
The problem is, there are a TON of surf bands. The good news is, many have samples on the web, so if you feel like Googling around, you can find plenty of resources to see what you like.
That being said, I humbly submit the following personal favorites...
Classic (60's era):
Dick Dale (self-proclaimed "King of the Surf Guitar" and considered by most to be the originator of the surf genre)
The Ventures (one of the most notable surf combos of the 60's)
The Shadows (fantastic British band)
The Astronauts (Like the Ventures, a standout band form the classic period)
Contemporary (but with very traditional 60's era sound)
Los Straitjackets (amazingly tight musicians who put clever twists on the traditional surf sound...sometimes considered "surfabilly"
Satan's Pilgrims (It's scary how much these guys sound like a classic era band...it's like they time-traveled from the 60's)
The Fathoms (Raw, traditional sound. Lots of twang and gritty saxophone)
The Galaxy Trio (fun, classic sound)
Contemporary (but slightly non-traditional)
The Aqua Velvets (These guys have a distinctive ethereal quality to their sound...really takes you places)
Laika and the Cosmonauts (wild stuff from Finland...great, unique sound)
The Halibuts (Good, traditonal sound with a bit of quirkiness)
The Bomboras (Could be considered "horror surf"...evocative of 60's-era scary movies)
Man or Astroman? (Traditional surf sound with heavy doses of classic sci-fi...I'd recommend their CD "Destroy All Astromen!")
Compilations
Rock Instrumental Classics, Vol. 5: Surf
Bikini World
Attack of the Killer Surf Guitars
Surf Guitar Greats: One Dozen Surf Guitar Instrumentals
Like Jahfin said, the Rhino "Cowabunga" box set is an excellent starting point, and the songs are arranged chronologically (roughly by decade), so you really get a sense of how the genre has evolved over the years.
Websites
There are several good surf-oriented websites. This first one has great surf/instro compilations available to download for free. I recommend the "Surfin' Knots" series:
http://sandgropers.blogspot.com/
Here's another great free downloadable compilation:
http://www.archive.org/details/SG101-2005_Mp3_Comp
And here are several other sites (record labels, reviews, etc.):
http://www.reverbcentral.com/
http://www.surfguitar101.com/
http://www.zptduda.com/cowabunga/index.htm
http://www.crickrock.com/cgi-bin/webrin ... eid=sandst
http://www.musickrecords.com/news.html
http://www.gollygeerecords.com/
http://www.dblcrown.com/
http://www.yeproc.com/