Powder compositions and articles and methods of forming articles from powder compositions are provided. In one embodiment the powder compositions include at least one polyester polymer powder and an amount of reinforcing particles having an aspect ratio of preferably at least about 5:1. In another embodiment the powder compositions include at least one medium-high melting temperature, aromatic and crystalline polyester polymer powder. In a preferred embodiment, the powder composition is capable of being formed, via a laser sintering process, into a three-dimensional article that exhibits one or more desirable mechanical properties in an elevated temperature environment.