I've been fortunate enough to have visited Maui half a dozen times now, every time basing myself in Kihei, which is located on the sunny south side of the island. It doesn't matter if you are a young single looking for a good time, a family of six requiring child friendly beaches, or a retired couple just seeking some rest and relaxation, Kihei has something for everyone.
Beginning at the north end of Kihei and traveling south towards Wailea there are a dozen or so beaches to choose from to plunk down for a morning or a day. Each one offers a different atmosphere and is uniquely beautiful. Want to beach comb and enjoy a quiet walk? Stay towards the north end and peruse Sugar Beach and Charley Young. Feel like people watching and enjoying almost year round mild swimming conditions with the security of lifeguards? Head to Kam I, II, and III. Desire a spectacular stretch of sand that is practically always uncrowded? Enter Keawakapu at either its north or south entrance and walk in either direction for your own little piece of paradise.
Keep heading south on S. Kihei Road and you'll enter Wailea, with it's ritzy resorts and hotels and likewise picture perfect white sand beaches. While these are not my favorite to visit, (preferring some of the more undeveloped and less crowded beaches in Makena), they are beautiful to behold, and the mile or so long walk in front of the hotels is a wonderful way to start your day (begin at Ulua/Mokapu beach and head south on a paved sidewalk that will take you all the way to the Fairmont Kea Lani. When I last took this walk there were two Manta Rays frolicking in the ocean just past Wailea point, and several sea turtles poked their heads up to say hello as I passed by).
Past Wailea into Makena, you will find some of the most beautiful, undeveloped, un-crowded and pristine beaches on the island. Chang's (unofficial name) is actually located to the right of Poolenalena Beach, down a dirt trail, over some rocks, and past some spectacular beach front homes. Never crowded, sometimes nude (there are some really private coves!) , and deserving of your most respectful beach etiquette, this is by far my favorite beach to spend the morning. Come early, and enjoy the peace and serenity of most likely having this remote and stunning beach all to yourself. Another Makena favorite (and surprisingly, only recently discovered by my family) is Maluaka, which sits adjacent to the Maui Prince Hotel. What a wonderful spot for families- relatively uncrowded, gentle swell for swimming (even my four year old was able to swim fairly far off shore) and great snorkeling at either end due to the rocky outcrops. Of course Big Beach (Makena Beach) is a must, even if you don't work up enough nerve to take on the huge swell. Especially at six in the morning, a walk along this completely undeveloped, white sand/turquoise water beach is like strolling through a Maui postcard.
Beyond all the beaches within easy walking or driving distance in Kihei, you'll be well placed to start any excursion you could dream of on your Maui vacation. It's a twenty minute drive from Kahului, a forty minute drive to Lahaina or upcountry to Makawao, and as it sits at the base of Haleakala the views in all directions are spectacular. There are several restaurants (definitely go to Kihei Cafe for both breakfast and lunch, and Maui Tacos for an inexpensive and delicious dinner). Cool outdoor markets for the perfect souvenir are located on S. Kihei Road, and there are surf shops, snorkel and scuba rentals, ABC stores, and grocery stores aplenty (Hawaiian Moon in the Dolphin Plaza has a pretty good selection of organic foods and even a hot meal deli). Safeway, off of Piilani highway, offers their discount card for free which will save you a bundle of cash on your grocery bill if you're staying in a condo and cooking for yourself. (My recommendation for budget friendly accomodations in a most ideal setting is the Maui Kamaole. Do your research online and book directly with owners through a site like VRBO for the best deals and most honest room descriptions).
Kihei is a fun, funky, beautiful, serene, low-key little beach town, and I think it represents the best of what Maui has to offer. Others may prefer the more resort like atmosphere of West Maui, the isolated wildness of East Maui (do yourself a favor and try to stay at least one night in Hana-nothing like it in the world), but for myself and my family, South Maui provides all the ingredients for a perfect vacation- great beaches, fabulous food, and true aloha spirit.