Quite a few mod already.
Don't forget the biggie driving style change, referred to around here as adjusting the nut behind the wheel, check out the 100+ hypermiling tips. If in the budget the Scan gauge or Ultra gauge are worth the money. They will pay for themselves in a short period of time the more miles you drive the quicker the payoff.
Great start! Don't forget to post your vehicle info and start a fuel log.