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The answer to your questions goes beyond a simple list. There are a number of species that nearly became extinct in large areas because of reproductive failure due to the pesticide DDT, including the bald eagle and the peregrine falcon. DDT caused the birds' eggshells to become so thin that they did not survive incubation. Populations of both these bird species have been restored through careful breeding and protection programs, but is was a narrow miss.
The Hawaiian honeycreeper known as the Po'o-uli is considered to be functionally extinct; a few birds still live in the wild, but none has a mate, and they all live in different territories that do not overlap. Since they will not leave their territories, they cannot find one another to mate.
The Florida cougar has, due to very small populations, become so inbred that all the surviving individuals are closely related. This has led to the reinforcement of some negative genes. As a result, the cougars have very low sperm counts, and the majority of the males captured for examination have at least one undescended testicle. In a lost-ditch attempt to preserve the species, biologists have found some cougars in other parts of the US that are genetically similar to the Florida cougar, and have crossbred them to introduce some new genes. However other biologists have criticized this approach, saying that the offspring are technically not Florida cougars.
Pandas are becoming extinct in the wild due to a number of factors, one of which is a very slow reproductive rate. In zoos, they are notoriously difficult to breed, so a captive breeding program is unlikely to help.
There are a few plants that are near extinction because of inbreeding. The best example of this is Potentilla robbinsiana, which grows only in the White Mountains of New Hampshire. In the early 1980s the species was down to about 50 plants all living in a small area, and all closely related to one another. Seed collection and hand rearing have allowed biologists to establish several new populations of the plant, but inbreeding is a problem which could still wipe out the species very quickly.
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