You don't need a special stain remover or laundry pretreater to banish a ring around the collar.
Whether it's on work shirts or Sunday best, staining around the collar can be easily vanquished with a touch of something you're pretty much guaranteed to have in the house -- shampoo. Just pour a little shampoo -- any shampoo will do, even the inexpensive, generic kind -- onto the collar, rub the collar together to work the shampoo in well, and rinse thoroughly. Then launder as usual.
For a convenient twist on this traditional tip, bring home the complimentary bottles of shampoo from hotels for a free package of ring-around-the-collar remover!