I'm not too familiar with Expositiones Mathematicae, but have you given them a look?
EDIT: The article I happened to have seen, which made me think that Expo Math might be along the lines Pete Clark was looking for, is this paper of T. Bühler - it modestly claims to no originality save for assembling disparate parts of the literature and writing down what's old news to connoisseurs (I'm paraphrasing here!) but of course this is, in a sense, precisely its originality & worth.
My preference is detailed pseudocode, at a high-enough level of abstraction to allow understanding the algorithm.
Of course, as pointed out by Ryan Budney's comment, it depends strongly on what the journal requirements are and in which journal you publish. However, I feel strongly that the complete code-set which you use should be available from some resource, either through the journal article's publsher, or from your own website, your academic website, or via Arxiv.
If the pseudo-code is detailed enough to allow reimplementing the algorithm straightforwardly by another mathematician, then that should be sufficient.
If the pseudo-code has to leave out certain details which are germane to the computation, then the interpreted code which implements the algorithm in a numerical computational package (such as Maple, Matlab, Sage, or Octave or Scilab (download link ) which are free open source software packages capable of running code similar to or equivalent to matlab) should be provided.
Why not provide both? -- If you can provide a link to your own webpage for the paper, or for its supporting supplemental materials, I don't see why you couldn't provide both the interpreted code and the compileable C or C++ code on your webpage, unless there are copyright issues involved such as if you did not write all of the code yourself and do not have the right to release all of the code source. I am a supporter of free open-source software and the Gnu organization's GPL licensing, which would allow others to benefit from your code and to contribute back to it via incremental improvements.
I suggest that you specify which version of software package, operating system, compiler, and/or library you used in running your program or in creating the binary application from your code. This is necessary because different versions of Octave (2.3 vs. 3.0) or Matlab (R10, R13, etc.) or any software package may implement or include different routines and may not be capable of correctly running your software program.
I would recommend that if particular packages are necessary in order to run the interpreted code in Octave or Matlab that you list which packages they are. In the same vein, if your C or C++ code requires particular libraries such as LAPACK or BLAS, make sure to list them in a text file or in a header file. If you know how to use the make program, you can create a makefile to help others in compiling your software.
The make program, the Gnu compiler collection, and many other development tools are all standard parts of Gnu/Linux distributions, such as Debian.
My preference is detailed pseudocode, at a high-enough level of abstraction to allow understanding the algorithm.
Best Answer
There is a method for doing this in the back of the TIkZ manual; you can put special commmands around a TikZ picture do have it make a separate PDF which you then include as usual graphics. I'll admit, though, that I've had poor luck using it. I'd rather just give an earful to any journal who doesn't like TikZ.