After a slight lull in triathlon action last weekend, the 2008 race season goes off the chain this Sunday, with big-time events shaking down everywhere from Cali to Columbia. Here’s a look at what’s on tap.

First up, the XTERRA season heats this weekend with the first of four regional championship races of the America Tour. After competing in various warm-up events across the globe, the world’s best off-roaders will converge on Temecula, California, for the XTERRA West championship, a gritty 1.5km swim, 30km mountain bike and10km trail run.

Headlining the men’s start list at Temecula is defending West champ, Conrad Stoltz of South Africa, who’s looking to build upon a stellar 2007 in which he won all but one regional before taking gold at the USA championship and Worlds. Challenging the Caveman for the West title will be last year’s race runner-up, Mike Vine of Canada, along with perennial American medalists Josiah Middaugh, Seth Wealing and Brian Smith. Another candidate to stir up trouble, Aussie Andrew Noble has had a hot spring with wins at XTERRA Saipan and XTERRA Guam and should be right in the mix for a medal. And a late addition to Sunday's start list, 2004 U.S. Olympian Victor Plata will toe the line in Temecula to give the full-time XTERRA dudes a run for their money.

For the women, look for three-time XTERRA world champion Melanie McQuaid to mop up on Sunday--that is, if she can outrace Colorado’s Jennifer Smith, 2002 XTERRA world champion Candy Angle, superbiker Shonny Vanlandingham and a back-in-action Danelle Kabush.

While the off-road junkies get down and dirty in Temecula, the long-course contingency will clash in Orlando for Ironman 70.3 Florida. As usual, this Walt Disney World classic has lured a strong crew of pros for its '08 edition, with defending champ Craig Alexander looking to keep his crown. Crowie should feel heat from last year’s fourth-place finisher, Bryan Rhodes of New Zealand, Minnesota bike master David Thompson, April’s Ironman Arizona runner-up TJ Tollakson and iron-vet Chris Lieto of California.

In the women’s race, 2007 champion and four-time Ironman winner Katja Schumacher of Germany will fight off charges from race-happy German Nina Kraft, Ironman 70.3 Worlds bronze medalist Lenada Cave, multi-distance star Joanna Zeiger and iron-glutton Dede Griesbauer.

On to the Olympic distance, two classic contests shake down Sunday in the Eastern time zone. First up, the Columbia Triathlon in Ellicott City, Maryland, has attracted several solid elites of myriad distance specialties, most notably 2007 Ironman world champion Chris McCormack. Greg Remaly, Paul Fritzsche, Eric Limkemann and Richie Cunningham will all challenge Macca for top honors, while the women’s race should be a total grudgematch, with long coursers Amanda Lovato, Desiree Ficker, and Linsey Corbin butting heads with U.S. Olympic team contenders Margaret Shapiro and Rebeccah Wassner.

Another popular springtime event, the Memphis In May Triathlon highlights the weekend. Notable names include Australians Paul Ambrose and Stephen Hackett, up-and-comer Andrew Starykowicz, and American elites Cameron Dye, Brad Zoller and Ben Hoffman. On the female front, triathlon legend Karen Smyers will race against Ironwomen Laura Tingle and Lauren Jensen.

Also on the schedule for the weekend are the Auburn International Triathlon and its corollary race, the World’s Toughest Half in Auburn, California, with mountain bike legend Steve Larsen and movie star-turned-triathlete Maxine Bahns topping the pro start lists. There's also the Shawnigan Half in beautiful British Columbia. As for International Triathlon Union action, there’s the Ixtapa Continental Cup in Ixtapa, Mexico, Saturday and the Brno European Cup in the Czech Republic Sunday. The islands host an Olympic-distance affair this weekend, as well, with the big-city Honolulu Triathlon.

You guessed it! Check back to InsideTri.com Sunday and Monday for full race recaps and photos.