Frankincense, Pine needles or resin (pitch), Myrrh, Juniper, Benzoin, Sandalwood, Copal, Cedar, Rose petals, Thyme, Bay, Basil, Cinnamon and Rosemary
Be aware that many plants (if not all!) smell quite different when being smoldered. Sweet scents turn sour fast.
If you wish, take a large number of dried and finely ground plant substances (flowers, leaves, bark, roots) and drop a small portion of each herb onto a hot charcoal block; then decide whether the scent is leasing or not. You might make a notation of each botanical and its scent in a special notebook reserved for this purpose or on three by five cards. Also note any psychic or other sensations you notice with each burning herb. In this way, you'll eventually build up a thorough knowledge of incense materials, which will aid you in your herbal magick.
Do remember that, as surprising as it sounds, scent isn't a factor in magical incense, except very generally: sweet odors are usually used for positive magical goals, while foul scents are used for banishing rituals.
Scent is power. It allows us to slip into ritual consciousness, thereby allowing us to raise power, infuse it with the proper energies, and send it forth toward the magical goal. However, not all magical incenses smell sweet. Some have strong, resinous odors; others, intensely bitter scents. Incenses intended for ritual use are blended to provide the proper energies during magical operations - not to smell pleasing to the human nose.
Don't let this scare you away from incense, however. Most of our associations with "pleasant" and "foul" odors are learned, and our noses aren't as capable of determining various scents as they should be. Retrain your nose to except exotic scents, and the art of incense burning will become a joy, not something to be tolerated for the sake of magick.
Occult supply stores stock incense intended for use in magick. Many rare blends can be purchased for a few dollars. While these are magically effective, you may wish to make some of your own.