Celebrate we will for DAVE MATTHEWS BAND, who performs with Southport, England, indie-rock band Gomez Mon., JULY 7, for the 2008 Live Nation Concert Series. DMB's first Atlanta appearance since last September's Piedmont Park benefit with the Allman Brothers, the jam band brings an ardent fan base to Lakewood Amphitheatre. What could be better for curing a case of the Mondays than singing along to "Two Step" with 19,000 fellow fans? $40.50-$75. 7 p.m. Lakewood Amphitheatre, 2002 Lakewood Ave. 404-443-5000. www.ticketmaster.com.