How many times have you found yourself stopped dead in your tracks, standing like an idiot in the middle of the sidewalk, staring at a particularly impressive piece of foliage, wondering, "What the hell kind of tree is that?" Wonder no more: The Sibley Guide to Trees, a full-color illustrated tome from the man who brought us Sibley's Birding Basics, gives you all the tools you need to identify more than 600 species of North American trees, from acacia to zelkova. $39.95. Annie Bloom's Books, 7834 SW Capitol Highway, 246-0053.

For occasions when a bicycle-lobby lapel pin is too formal and a "Screw You and Your Hummer" shirt is not quite formal enough, this bicycling beaver T-shirt by the Bicycle Transportation Alliance is just right. The yellow says "fun," the beaver says "Oregon," and the 10-speed it's riding says "I'm not a fixie-riding scofflaw, so please don't run me over." $20. Land, 3925 N Mississippi Ave., 451-0689,

So you're heading out on a three-week trek along the Pacific Crest Trail and you want to take the GPS unit, cell phone and digital camera, all of which have different proprietary batteries. How do you keep them charged? The Voltaic Systems Backpack incorporates three tough solar panels into a 1,850-cubic-inch backpack made from recycled soda bottles. The panels put out 4 watts of power at 10 volts that can be used directly or to charge the included battery, with three voltage output levels and a small zoo of adapters for mobile devices. The whole thing is remarkably light and comfortable—worth the hefty price. $299. Seven Planet, 412 NW Couch St., 575-9455,

Portlanders tend to think of the Willamette River as a brown strip of occasionally toxic water between Oregon City and Sauvie Island. But there's a lot more to it than that. In The Willamette River Field Guide, Travis Williams, executive director of Willamette Riverkeeper and winner of a 2004 Skidmore Prize, explores the Willamette from its headwaters at Waldo Lake right up to its confluence with the Columbia River at Kelley Point Park. Packed with paddling itineraries, landmark histories and breathtaking photos, the Field Guide is a comprehensive work about the magnificent, troubled river, as well as an indispensable reference for would-be explorers. $24.95. Powell's City of Books, 1005 W Burnside St., 228-4651,

Of the many troubles facing the fashion-conscious Portland bicyclist, helmet hair is surely one of the most harrowing. If you wear a helmet, you'll end up with a sweaty, matted coif; if you don't, you'll die. This waterproof Portland Cap, from local designers Showers Pass, neatly solves the dilemma. While you're riding, it keeps your head dry and rain out of your eyes. Then, when you take off your helmet, you're wearing a nifty hat. Everybody wins! $39, River City Bicycles, 706 SE Martin Luther King Jr. Blvd., 233-5973,