std.logger

String logging facilities for Phobos.

Docu:
http://burner.github.io/phobos/phobos-prerelease/std_logger_core.html
http://burner.github.io/phobos/phobos-prerelease/std_logger_stdiologger.html
http://burner.github.io/phobos/phobos-prerelease/std_logger_filelogger.html
http://burner.github.io/phobos/phobos-prerelease/std_logger_multilogger.html
http://burner.github.io/phobos/phobos-prerelease/std_logger_nulllogger.html
http://burner.github.io/phobos/phobos-prerelease/std_logger_templatelogger.html

dub
http://code.dlang.org/packages/logger
I would even go further, classes shouldn't be mandatory at all.
A Logger should be a concept and `log(Logger, Args...)(Logger logger, lazy Args args) if (isLogger!Logger)` should work with anything that fits the concept (duck-typing).