Answer: Be warned: most rapidly-spreading ground covers can be invasive, and take over adjacent garden beds and lawns.
Creeping sedum (Sedum acre) grows to 2" high, and is a very vigorous grower on sunny, dry sites. It can be quite invasive. Snow in summer (Cerastium tomentosum) grows up to 6" tall, and spreads quickly. Roman chamomile (Chamaemelum nobile) has similar characteristics.
Wooly yarrow (Achillea tomentosa) grows to 6-12", and is easily established in hot, dry areas.
Bearberry (Arctostaphylos uva-ursi) is a low growing, creeping shrub that grows to a height of 6 to 12", forming dense mats. It prefers full sun and sandy soil. Creeping juniper is another possibility.
Hope this helps.
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