Is there something she has always wanted to try? If so, give her the gift of an experience - for example, if she has always wanted to try sky diving, take her sky diving. (Okay, that's an extreme example, but you know...) Or if there is a hobby she wants to take up, buy her the supplies or equipment. My mum was into photography but wanted to start taking movies so for her 50th I bought her a camcorder.

A spa day gift would be good. Most Moms dont get the time to do some serious pampering and might feel guilty if they did. But if you give them a gift of a spa day they can have some serious pampering guilt free for hopefully what will be a wonderful birthday celebration