Annabel is currently teething, we haven't actually got a tooth yet but she has all the signs of one of those little nippers soon appearing.
I've found that giving her really cold food is soothing for her. I have pureed a number of fruit based dishes (see recipe exchange thread) that I keep in the freezer, I remove one/two in the morning and place in the fridge. By the time we are ready to eat them they are really really cold but defrosted, perfect to help painful and swollen gums.
If doing baby led weaning a tip would be to place sliced pieces of fruit in the freezer or the fridge and then let your LO suck and nibble on them.
If you think that your LO has pain and is struggling to eat then try calpol (dose according to the bottle) about thirty minutes before feeding.