Local resources include:
Swing, The Washington Post's online guide. Interactive map with local courses, feature articles, equipment reviews, tons of content.
Waggle.com, a website filled with regional golfing resources including hundreds of course reviews and updates on local events.
The Washington Post Sports section on Mondays. Buy the hard-copy edition and most Mondays you'll find golf course discounts. I haven't done a survey, but tragically, most seem to be for weekdays. Not always though--I saw a recent Bowling Green (Front Royal, Va.) discount for $25 on weekends after 1 p.m., compared to the usual $39.
Pros 'N Hackers magazine. This is a good quirky regular-Joe publication on its own merits, but I'll bet most of us subscribe to get the discounts offered every issue. I'm counting 21 discount coupons in the May, 2006 edition. The best deals are for weekday play, but many are for weekend afternoons. One random example: As of this post the excellent inland links course Bristow Manor, outside Manassas, charges $65 a round on Saturday and Sunday mornings; the Pros N' Hackers discount was for $35 anytime Monday through Thursday and Friday, Saturday and Sunday after 1 p.m. Other discounts are available when you subscribe. This year I chose the $49.99 option, which included a round "any day, any time" at the new Laurel Hill in Lorton. That's a $79 round during prime time weekends. A similar deal, with a few restrictions but still usable on weekends, was offered as of post time for Renditions in Davidsonville, Md., which normally peaks at $89 a round. You can also pay $20, forget those deals, and just get the regular monthly discounts. Nine issues a year. You'll find free copies, absent all the discounts, available at many local driving ranges and courses.
GolfStyles Washington is a higher-end publication that's part of a chain. If you like reading about luxury golf vacations and the downside of country club memberships, this is the monthly for you. Well-edited with some useful directories and relentless updates on its "Solstice Survival" 54-hole competitions. Free subscription.
SkyCaddie by SkyGolf. Why am I including a national product on this local list? Because SkyGolf, a GPS-based handheld device that maps distances to greens and hazards, has a ton of local tracks in its database. You can search that database without spending a dime. The unit costs around $349, and annual subscriptions run from $19.95 to $59.95 a year, depending on how many courses you want in your library (sorry--I mean Sky Vault. Kind of like Fort Knox, where you may need to go after paying for everything). I'm addicted to mine.
Golfwits is another mapper I've used. Plenty of local courses on their list too. They have both PDA- and downloadable hard-copy maps--print it out, cut it up, staple it together, stuff it in your pocket. Though not GPS-based, the hard-copy color maps I've used are visually easier to navigate than the adequate SkyCaddie display (other than the simple but very usable graphics for the greens, SkyCaddie hazard instructions are sometimes inscrutable). Even without digital readouts of your yardage, these are very useful aids, especially if you choose the option to mark 100-, 150-, and 200-yard arcs from the green. If you use the PDA software, you can compile a depressing complexity of stats on items like greens in regulation, sand saves, and lost golf balls "good" double-bogies.
TeeTimes.com Pay $26 a year and book times up to 14 days in advance. Biggest drawback: Limited courses in this area. On the Virginia side, as of May 25, 2006 you'ree limited to to Algonkian, Brambleton, Burke Lake, Forest Greens, Generals Ridge, Greendale, Jefferson District, Laurel Hill, Oak Marr, Pinecrest, Pohick Bay, and the two Twin Lakes courses (Lakes and Oaks). That's much better than nothing, but I count 67 courses in my own NoVa/DC/Maryland directory. I see nothing in Tee Times for the Disctrict of Columbia, and 11 courses in Maryland, but over towards Ocean City and the like. Other Virginia courses are available around Williamsburg. TeeTimes.com is in several other states, with a decent selection in the Pinehurst/Sandhills region and some in North Carolina's Outer Banks. There's a special section at TeeTimes for Northern Virginia courses, so pay attention when you sign up.
Singles Golf DC if you're, you know, single. Also known as the Washington, D.C. chapter of the American Singles Golf Association. I don't have any experience with them (yet), but judging from their current schedule they're very active with regular weekend and mid-week outings and clinics, a number of which are concluded with post-golf analysis at local watering holes.

