OsMoz: Olfactory Groups – gives definitions of olfactory groups and examples of fragrances that fit.
Raw Materials – grouped by "smell", with odour profiles for each ingredient.

Perfumers Apprentice: Aroma/Flavor Molecules – a store to buy aromachemicals, which also gives smell profiles.
Natural Essential Oils & Absolutes – smell profiles for the natural ingredients.

Essential Oils – provides information about where fragrant essential oils come from, their structure, and their uses.

Basenotes: Directory – 1000s of fragrances with reviews from members of the community.
Community – place to talk scent.
Note Pad – descriptions of raw materials by the BN community.

The Dry Down – RSS feeds from fragrant blogs.
Perfume Search – search engine for perfume reviews.