Here is a research on similarities in Greek philosophy and Indian yoga (in broad sense):
The Shape of Ancient Thought: Comparative Studies in Greek and Indian Philosophieshttp://books.google.com/books?id=Vpqr1v ... frontcover
To my opinion some similarities presented in this book are just similarities, but there is also some evidence of borrowing.
It seems that at least part of Greek philosophy was what in India would be called "yoga" - or "personal development" and "self-improvement" in modern times. Pyrrho(nism), Stoicism, Cynicism, Epicureanism, (Neo)platonism - all these included ethical systems (sometimes involving asceticism) and mental training aimed at reaching dispassionateness and happiness. If not inspired by, these philosophies were at least influenced by Indian samana teachings, - probably including early Buddhism.