Difference between еще and ещё?
Is there any difference among them?
Nope. Some Russian speakers write е instead of ё.
(EDIT: Accidentally typed the reverse of what I meant.)
That is correct. Eще is an acceptable (mis)spelling of ещё. Russian speakers usually don't care: we know when a е is a е and when it's a ё, but I find it irritating that the phonetic nature of Russian is given away so easily over something completely irrelevant these days: some historical typographic issues with typesetting ё.
From everything I've read, the two little dots above ё are sometimes left out by natives and are pretty much only used in children's books, dictionaries, and certain city signs for tourists. Natives would know whether it's suppose to be e or ё and don't need the dots to know to say ye or yo. So еще is just an acceptable spelling of ещё, but still pronounced ye-sch-yo. Ye-sch-ye would not be right and is not a word.
but still pronounced ye-sch-yo
No, it isn't! There is no second "y" sound there! If anything, it's "ye-sch-o" (assuming "sch" stands for palatalised "sh", although the standard English "sh" is sufficiently palatelised as it is).