I think it depends on what sounds best as well as what the people who made the acronym had in mind. I have personally never heard anyone pronounce ASP as one word. To me, it actually sounds derogatory when said like that(maybe I should start using it then
). A-S-P, however, sounds more professional.
PHP could be pronounced as "fip", but that just sounds awkward. Conversly, SQL is sometimes pronounced as Sequel, which doesn't sound bad at all. I personally prefer S-Q-L, though, since that's the ANSI standard and I like it more.
I think this can best be summed up with a quote from Donald Knuth:
"The most important thing in the programming language is the name. A language will not succeed without a good name."