There are a few companies that make the powered speakers. Some of these would include Yamaha, Prosound, as well as QSC. More information can be found on the website PreSonus.
There are several different companies that make 4 x 6 speakers. Some of the best companies which are offering the 4 x 6 speakers are Pyle, Polk companies.
A number of well known companies make well known tower speakers. Some companies that make them include Sony, Pioneer, Yamaha, Bose and Logitech. One can purchase most of them from Amazon.
Mackie powered speakers can be purchased from websites such as Amazon and eBay. Some other online stores such as zZound, SweetWater, and SameDayMusic also have Mackie powered speakers available for sale.
Some cheap speakers for your computer include the Geeks 2 Piece USB Powered Speaker Set for $3.99 or the VIBE Ultra Thin USB Powered Set or the iMicro USB Powered set.
There are many companies that offer a motivational speakers bureau. The most successful and famous company that offers a motivational speakers bureau is Premiere Motivational Speakers.
Apple does not make portable speakers for ipods but other companies such as sony and logitech do. They work great, some better than others. Testing products help pick the right one as well.
There are some companies like Texas Industries that make solar powered calculators, but other than that I don't really know.
If one is interested in good outdoor speakers, it is recommended to check Good Outdoor Speakers Depot's website. They offer some of the best speakers at a fair price.
PA speakers are made by several companies. Yamaha is one of the better known manufacturers. Hollinger, TOA, and DJ systems are also avaiable. Outdoor PA speakers are made by Liberty, Explorer Pro and Beacon, to name a few.
Black & Decker and Rubbermaid are two companies that make a combination travel cooler and warmer. They are kept cool and warm through a thermo-electric system and are powered by plugging them into your vehicle's accessory outlet.
You DO NOT need an amplifier for a dj setup. Some speakers now come with a built in amp, known as a "POWERED SPEAKER".
Pioneer does make some MP3 speakers. They offer a great variety of different types of MP3 speakers that can be used in your car or in the comfort of your own home.