There's a lot of great music and sound effects that very talented musicians and sound designers make available for free. All they want in return is acknowledgement. I don't think VO really help out Indie games. I actually prefer text so I can go at my own pace and don't have to worry about misunderstanding a strong accent, for example.
I think AI is more useful for boring and tedious tasks. For example, if I could get an AI to play test my game or just tell me where the bugs are. Now, that would really help out.