There are three main hardware categories for bitcoin miners: GPUs, FPGAs, and ASICs. We'll explore them in depth below.
CPU/GPU Bitcoin Mining
The least powerful category of bitcoin mining hardware is your computer itself. Theoretically, you could use your computer's CPU to mine for bitcoins, but in practice, this is so slow by today's standards that there isn't any point.
You can enhance your bitcoin hash rate by adding graphics hardware to your desktop computer. Graphics cards feature graphical processing units (GPUs). These are designed for heavy mathematical lifting so they can calculate all the complex polygons needed in high-end video games. This makes them particularly good at the SHA hashing mathematics necessary to solve transaction blocks.
You can buy GPUs from two main vendors: ATI and Nvidia. High-end cards can cost hundreds of dollars, but also give you a significant advantage over CPU hashing. For example, an ATI 5970 graphics card can give you over 800 MH/sec compared with a CPU, which will generally give you less than 10 MH/sec.
One of the nice things about GPUs is that they also leave your options open. Unlike other options discussed later, these units can be used with cryptocurrencies other than bitcoin. Litecoin, for example, uses a different proof of work algorithm to bitcoin, called Scrypt. This has been optimized to be friendly to CPUs and GPUs, making them a good option for GPU miners who want to switch between different currencies.
GPU mining is largely dead these days. Bitcoin mining difficulty has accelerated so much with the release of ASIC mining power that graphics cards can't compete. If you do want to use them, you'd best equip yourself with a motherboard that can take multiple boards, to save on running separate PSUs for different boards.
FPGA Bitcoin Mining
A Field Programmable Gate Array is an integrated circuit designed to be configured after being built. This enables a mining hardware manufacturer to buy the chips in volume, and then customize them for bitcoin mining before putting them into their own equipment. Because they are customized for mining, they offer performance improvements over CPUs and GPUs. Single-chip FPGAs have been seen operating at around 750 Megahashes/sec, although that’s at the high end. It is of course possible to put more than one chip in a box.
ASIC Bitcoin Miners
This is where the action’s really at. Application Specific Integrated Circuits (ASICs) are specifically designed to do just one thing: mine bitcoins at mind-crushing speeds, with relatively low power consumption. Because these chips have to be designed specifically for that task and then fabricated, they are expensive and time-consuming to produce - but the speeds are stunning. At the time of writing, units are selling with speeds anywhere from 5-500 Gigahashes/sec (although actually getting some of them to them to ship has been a problem). Vendors are already promising ASIC devices with far more power, stretching up into the 2 Terahashes/sec range.
