Question: Does "подруга" mean girlfriend as in "girl friend", ie a female friend, or as in "girlfriend", a romantic interest?

Doing a google image search for подруга seems to be getting matches for both types.

Answer: 
"Girlfriend" and "boyfriend" are most usually conveyed in Russian as *девушка* and *парень* (or *молодой человек*).

*Подруга* usually means "girlfriend" as well but its meaning is somewhat less suggestive of a romantic relationship than that of *девушка*.

As a male you do not call your female friend *подруга*, not without raising an eyebrow. Women, on the other hand, could refer their female friends as *моя подруга* (while using *моя девушка* would unequivocally imply romantic relationship with her).

If you want to rule out any romantic component in describing your friendship, you should use *знакомая* ("acquaintance") or *приятельница* (female equivalent of "buddy").
In addition to other answers (especially Quassnoi's) 

1. From time to time old-fashioned peoples (like grand parents) can use '*подруга*' in meaning "girlfriend":

	* У него есть подруга (He has a girlfriend?)
	* Нет (No)
2. Also when you talking about specific women, you can use "*подруга*" in meaning GF:

	* Итак, Джулия... она твоя подруга? (So... Julia, is she your GF?)
	* Нет, просто друг. (No. Just a friend)
3. Between man and woman "*подруга*" can means "GF" or "friend".
4. Between woman and woman "*подруга*" will be always means "friend".
5. "Подруга" it's an undefined state. If you'd way 

	* Она моя подруга (She is my )

Usually people would ask you:

* Девушка? (A girlfriend?)

Cause your relationship isn't clear for them.

6. If you want to introduce a woman as a friend, it'll be better to say "*Друг*" ("friend")

Она мой друг. Мы друзья. (She is my friend. We are friends)