I know you're supposed to use rel="nofollow" on outgoing ads, to keep from passing link juice, but what about internal ads? We have a number of links with pictures that I consider as ads to other parts of our site (usually to a sub-domain). Should I rel="nofollow" them? With google's most recent algorithm change this month, I feel like some things have changed.
No, you should always avoid* using use
rel="nofollow" on internal links. Matt Cutts wrote about this a while back.
Of course, things might change in the future, but as of today, that's Google's advice.
*As per @Mike's comment, "avoid" is a bit strong - "don't bother with" is probably more suitable.