Here is an exact excerpt from PHb 3.5: "Druids are proficient with the following weapons: club, dagger, dart, quarterstaff, scimitar, sickle, shortspear, sling, and spear. They are also proficient with all natural attacks (claw, bite, and so forth) of any form they assume with wild shape (see below). Druids are proficient with light and medium armor but are prohibited from wearing metal armor; thus, they may wear only padded, leather, or hide armor. (A druid may also wear wooden armor that has been altered by the ironwood spell so that it functions as though it were steel. See the ironwood spell description, page 246) Druids are proficient with shields (except tower shields) but must use only wooden ones. A druid who wears prohibited armor or carries a prohibited shield is unable to cast druid spells or use any of her supernatural or spelllike class abilities while doing so and for 24 hours thereafter."
Therefore, if a druid does have pre-existing weapon proficiencies, she may use those weapons. This actually answered a question I had about a druid using a falchion, which is stated to be simply a large version of a scimitar.