Depends on whether you can just say nothing (rather than actually telling a lie) - that would be my preferred option!
Friend's haircut? If asked, I'd probably say I had really loved it the way it was before rather than say I hated it now.
Kids' pictures - none of my friends have kids young enough to worry about that one (and they would know better than to let the kids anywhere near me).
I try to be tactful, but I don't tell outright lies very often*. I don't lie (or even try to be all that tactful) with my Squeeze.
* I did tell two woppers on Saturday, but I am trying to sell my flat!
I can't think of a time when I've felt the need to be anything but honest at work, but sometimes need to be diplomatic.
Edited: 14/08/2012 at 14:46