Guitar Center discounts a selection of guitars, amps, and accessories during its Guitar-A-Thon. Shipping starts at around $5, or get free shipping on orders of $25 or more. (In-store pickup may also be available.) Acoustic guitars start at $49.99, electric guitars start at $69.99, bass guitars start at $129.99, and folk instruments start at $29.99. Deal ends May 10.