Is there a default location for 'linux too applications'
The short answer is, unfortunately, no there isn't a default location.

But it's not complete chaos.

For command line tools that ship with the OS or get brought in by Apple-supplied applications like Xcode, you'll find it all in /usr/bin. That includes things like the OS X default Python and Perl as well as the Xcode-supplied gcc, clang, make and the other command line developer tools Xcode installs.

For non-Apple command line tools, if the application is well-behaved, it should put them in /usr/local/bin.

Some .app packaged applications that install under /Applications offer command line tools (for example subl offered by Sublime Text 2). If I want to use these from the command line I'll generally make a symlink from /usr/local/bin to the tool under the .app file for the application rather than put the application-specific path on my PATH environment variable.

If you use a package manager like Homebrew to install and manage your command line tools then it's not too much of a hardship to make /usr/local/bin the place for everything you use. Homebrew does a very nice job of keeping it neat and clean and all in one place for you. I can't speak to how well MacPorts or Fink keep things contained under one sub-tree like this.

The exception to the rules are OS X-default daemons like Postgres and such. Those can get scattered and there really isn't a very good way to track them down aside from find and maybe mdfind from the command line.