Watch out FedEx, UPS, and Amazon. The US Postal Service is expanding same-day deliveries, shipping things like groceries, water, and fish to customers in seven cities, in order to compete with its competitors and boost revenue under new postmaster general Megan Brennan, report the Wall Street Journal and Consumerist. Brennan is also looking to expand Sunday deliveries and overturn an odd Prohibition-era ban that blocks the postal service from shipping booze. USPS hopes the change could add $50 million in revenue. (More US Postal Service stories.)