First Aid is an important skill that every scout should know. It should be noted that first aid is not the definitive medical care/treatment, but the first assistance you can give to an injuried person. The following are some ebooks on first aid that should help brush up your knowledge. It is important to attend a first aid course if you wish to practice first aid, and not depend on these ebooks only.
eBook: Simple First Aid [ original copy | mirror copy | 32.3KB | Source: ScoutBase UK Factsheets ]
eBook: First Aid Guide [ download copy | 454KB | Source: Unknown ]
More external resources: BBC Health, First Aid Index, First Aid on your Mobile, First Aid Training Book