Rather than spending money on purchasing a gift, give some thought to your talents and how you might be able to "give in kind" to the couple. Case in point: a graphic designer could offer to design wedding invitations, a tech-savvy friend could offer to assemble a photo slideshow to be shown during the reception, or a music enthusiast could offer to perform during the ceremony or DJ the party.
If traveling out of town to attend a wedding, make sure you take advantage of preferred rate "wedding blocks" set up by the host couple at one or two hotels close to the venue. Or if a wedding block has not been arranged, call nearby hotels and ask if they offer a "Social Rate", which will usually save you $50-$100 off the typical rack rates.
Don't leave your wedding gift purchase until the last minute! Shop early and save by choosing the more reasonably priced items on a registry. If you wait to the last minute, you might be stuck with paying for a pricey set of crystal or a silver tea service rather than the more reasonable set of towels.
Talk to friends attending the same wedding to see if they might be game to go in on a gift together. Rather than spending $150-$200 for an individual gift for the couple, you can pool your funds (say five friends, times $100 each) and get a really GREAT gift for the couple.
At the start of each wedding season, invest in one great outfit that you can wear to multiple weddings by changing accessories for a slightly different look.