Gingko

Name: Ginkgo
Scientific name: Ginkgo biloba

Possible uses: prevention of Alzheimer's disease, mood elevation, tinnitus, alertness, memory enhancer, ability to concentrate, dizziness, anxiety, lung ailments (seeds), peripheral, arterial occlusive disease, vertigo, asthma, allergies, inflammation

Part of plant used: seeds (after removing the flesh), leaves

Possible side effects: diarrhea, irritability, restlessness, contact dermatitis (seeds and fruits-best use gloves to avoid this problem)
Active constituents: ginkgolides

So, according to Green Pharmacy, there was a study conducted that showed that gingko improved blood flow to the brain (probably why it helps with the prevention of Alzheimer's).  This herbal is interesting because, for the leaf extract, you have to get the standardized extract, you can't use just  plain ginkgo extract.  The seeds are eaten in South Korea with rice sometimes, so there's no need for to use these just for their medicinal properties.  Caution that if not prepared properly, the seeds can be toxic.
This herbal can inhibit PAF (platelet activating factor), which is essential in triggering allergies, asthma, and inflammation.

Sources

Refer back to the Sources post to see the exact books that I used!

Eastern/Central Medicinal Plants and Herbs

Taylor's Guide in Herbs

Green Pharmacy

Clinical Articles
Role of Ginkgo biloba extract as an adjunctive treatment of elderly patients with depression and on the expression of serum S100B
Effect of Garlic, Gingko, and St. John's Wort Extracts on the Pharmacokinetics of Fexofenadine: A Mechanistic Study
Your questions about complementary medicines answered: gingko biloba.
Effect of acetazolamide and gingko biloba on the human pulmonary vascular response to an acute altitude ascent.
Interaction between warfarin and Chinese herbal medicines.
Effects of herbal extracts on the function of human organic anion-transporting polypeptide OATP-B.