List of online C++ compilers

I have been using the online C++ compiler, codepad, for the last few years to quickly test small bits of C++ code. Then I came across another one, Ideone, and then another and another and... until I needed to keep a list of them. There are other lists out there—in fact I started with the this one—but some aren't kept up to date or are incomplete. I needed my own list, so here it is, from best to worst, according to my admittedly cursory review.

Ideone	GCC	Great!
Koding	GCC registration	Impressive, but might be too ambitious.
codepad	GCC	Basic.
Rextester	Clang GCC VC++	Basic.
HackerEarth	GCC	Basic.
Wandbox	Clang GCC w/Boost	Basic, but can change compiler command-line options.
Coliru	Clang GCC w/Boost	Basic, but can change compiler command-line options.
C++ shell	GCC w/Boost	Simple.
GCC Explorer	Clang GCC Intel ICC	Basic. Just compiles code and displays assembly-language output.
dbgr.cc	GCC	Hmm... Can debug your code! But they plan to charge.
WebCompiler	VC++	Microsoft's online Visual C++ compiler. Rudimentary, but can change compiler command-line options.
Coding Ground	GCC	Would be "Good" if console output wasn't duplicated 4 or 5 times.
Online Compiler	GCC	Crude. Doesn't run the code—you download the executable.
bOtskOOl	? registration	I never received the registration confirmation email.
CodeTwist	?	Like a codepad "lite." JavaScript error when I tried to use it.
Comeau	Comeau	Crude, 90's web design. Currently down. Compile only?

I did something sort of like this twenty years ago. I had written a static-analysis tool for C (not C++) built on top of an extensible C parser I also wrote. I was playing around with sendmail at the time. I wrote a sendmail rule that ran the analysis tool on any C code in the body of an email sent to a particular email address and returned the resulting report to the sender.