Evergreens:
Junipers naturally grow in many dry environments, from rock outcrops to sand dunes, therefore they are well suited to the xeriscape. Yuccas are a plant that do best if they aren't watered (once established). They grow a long taproot and will be able to find all the water they need on their own. Yuccas look like a desert plant with their spiky, pointed leaves. They also have very showy 150 cm - 175 cm (5' - 6') tall flowers that appear in July.

Trees & Shrubs:
Ash and Honey-locust are two shade trees that can withstand drier summers and a wide range of soil conditions. Turkish Hazel, though not as well known, is an excellent choice for drier sites. It grows 12 m (40') tall, has a broad, pyramidal shape with interesting corky bark, and dark green foliage that turns yellow in October.
Some larger shrubs are also drought-tolerant. Examples are Russian Olive (mature height 7 m (23')), Devil's Walkingstick 5 m (16'), Sea-buckthorn 4 m (13'), and Sumac 5 m (16'). Smaller shrubs like Bayberry, Honeysuckle, Butterflybush, and Caryopteris are also good choices for a dry garden.

Annuals:
For continuous summer colour, plant Celosia, Amaranth, Gomphrena, Sunflower, Zinnia, Portulaca, and Gazania. Mix in Dusty Miller to provide contrast with its grey leaves.

Perennials:
This is a large category where plants are divided into "moderately" drought-tolerant and "very" drought-tolerant. The first group includes Artemisia, Red Valerian, False Indigo, Daylilies, Lavender, Red-Hot Poker, Russian Sage, Thyme, Marguerite Daisy, Sea Lavender, Wall Cress, Basket-of-Gold, Rock Rose, and Creeping Baby's Breath.
Some very drought-tolerant perennials with succulent, fleshy foliage are Prickly Pear Cactus, Sedum, Hens & Chicks (sempervivum), Purple and Yellow Ice Plant, and Donkey-tail Spurge. Other drought-tolerant perennials suitable for xeriscape include Sea Thrift, Butterfly Weed, Gloriosa Daisy, Blue Flax, Liatris, Edelweiss, Blanket Flower, Sea Holly, Purple Coneflower, Thread-leaved Coreopsis, Blue Seakale, Yarrow, and Perennial Bachelor's Button. Some of these are actually hard to grow in a watered garden, because their roots are very likely to decay in moist soil!
Because lawn grass is shallow rooted and, therefore, burns off in hot dry summers unless consistently watered, drought-tolerant ground covers may be more practical. Crown Vetch and Goutweed will cover a large area very quickly (Caution! These two are almost unstoppable!). For smaller areas, use Lamb's Ears, Creeping Phlox, New Zealand Burr, Pussytoes, and Snow-in-Summer.
Finally, some Ornamental Grasses are deep-rooted and suitable for xeriscaping include Mosquito Grass, Lyme Grass, Fescue, Blue Oat Grass, Oriental Fountain Grass, and Feather Grass. Big and little Bluestem, and Switch Grass (Panicum) are beautiful North American natives that get by on very little water.

Establishing Drought Tolerant Plants:
One way to lessen the frequency of watering any part of your garden is to incorporate a lot of organic matter like peat moss, manure, and compost into the planting bed. Not only does this create a more fertile soil but the organic matter holds onto moisture making it available to plants for a long period of time after rain (or watering). You can also cover the soil with 5 cm - 10 cm (2" - 4") of mulch such as bark chips, cedar mulch, or cocoa bean mulch to minimize moisture loss through evaporation. (The mulch also makes it more difficult for weeds to get established.)
In their first year, your xeriscape plants will need supplemental watering during dry periods. After 5 to 7 days without water, use a trowel to check the soil and if it is dry four inches down, water deeply. It's in the second and subsequent years you can let them go for 10 days to 2 weeks (or longer) between deep waterings (i.e. water needs to penetrate the soil to a depth of 10 cm (4") to do any good). It's best to water in the morning before 10 a.m. or in the evening after 6 p.m. so water doesn't evaporate during the hottest hours of the day. (Keep the leaves of your xeriscape plants dry when you water them!) Watch for signs of wilting or leaf burn to determine if you need to water a bit more often. Some summers can be very long and dry and even your "drought-tolerant plants" may need a bit more care during these extreme conditions.