I work as a literacy tutor in a preschool and part of my job is to help students develop phonological awareness by teaching them how to identify rhymes and alliteration. To make it as easy as possible for kids who are first learning I'd like to find the phonemes in English which are the easiest to tell apart. Not sure of the answer to this question I've been trying short (plosives) vs long (vowels and fricatives) phonemes, and voiced vs unvoiced phonemes. I'm also avoiding phonemes with the same tongue position (f/v, s/z). Does anybody have any information on this topic? Is there any research on the topic? Thanks.
Yes, there is a lot of research on phoneme confusability. Here is just one of many similar papers on the topic:
Cutler, A., Weber, A., Smits, R., & Cooper, N. (2004). Patterns of English phoneme confusions by native and non-native listeners. The Journal of the Acoustical Society of America, 116(6), 3668-3678.
The PDF is available at http://pubman.mpdl.mpg.de/pubman/item/escidoc:60592:2/component/escidoc:60593/Cutler_2004_patterns.pdf.
You may find Table I and Table II helpful, specifically.