Letterheads and business cards are a requirement for most businesses. These promote credibility to your business as well as provide a current or potential client with contact information. The primary concern would be the design and the quality of stock paper for the business card. With the low cost to print business cards, I recommend getting a design done and sending it to a local company such as FedEx if you are in the U.S. or find the equivalents if you are not.
The design for a business card and stationary should adhere to your overall branding in order to consistently promote your business. The deviation away from your business logo and the amount of information contained would depend on your business model. In some cases, the business card may contain a coupon to not only give customers your contact information but to promote as a sale down the road.
The biggest consideration outside of the design for stationary and business cards would be the paper the design is printed on. A low quality paper stock or thickness will save you money, but may not promote a level of professionalism that business cards printed on a thicker stock will. The advantage of using a local company is that, it is not possible to feel for thickness and quality of the stock paper when ordering online.
Quantity would not be as much a consideration with letter heads as this would most likely be used to create general or specific documents based on an electronic template. Stationary printing companies do offer quantity discounts for business cards, but I find that in most cases, anything over 500 cards end up being a waste of money. This is especially true now a days when client / customers are more likely to share business information electronically.
Miscellanies promotional items:
Keychains, ball pens, coffee cups and other branded promotional items can be effective ways to promote you brand. There are many web based companies that specialize in this area, and the cost would depend on the quantity. These are perfect for trade shows or businesses that have physical locations that can be handed out directly to customers. They can also be included as free giftsor included in an order.