Another back issue of Sino-Platonic Papers has been released as a free PDF: Chinese Romanization Systems: IPA Transliteration (1.34 MB), by Warren A. Shibles. This was first published in November 1994 as SPP No. 52.
This work, whose rather dim view of romanization I do not share, is primarily a useful compilation of various published forms of IPA transcriptions for all the syllables of Mandarin. To these the author adds his own stab at applying the International Phonetic Alphabet to Mandarin. Moreover, a variety of romanization systems are shown, including that from Werner Ru?denberg’s Chinesisch-deutsches worterbuch.
I hope that the variety of approaches will provide a useful reminder that standard Mandarin is represented by a range, not a fixed point. And also that standard Mandarin is not the same thing as a caricature of a Beijing accent. Too often, in their quest for “correctness,” students of Mandarin end up with so many ers that they sound like they’re part circus seal. Emulating the sounds of the Beijing dialect of Mandarin is fine (though generally unnecessary); just don’t go overboard.