Idiot's Guide to FPGAs Please!

I know absolutely nothing about FPGAs. So, is there a real idiot's guide somewhere that will help me understand the most basic details of what these devices are, how they work and what they can do? I have tried looking on the web but as usual, everything I find assumes that the reader knows the basics. I cannot even find out whether they have processors or if they are just logic gates!

By background, I actively write software in Visual Basic 6 with APIs written in a mixture of C++ and ASM. Specifically, I am interested in Genetic Programming and typically to find a solution my programs may run overnight or even for a week or so. This despite the fact that they are optimized for speed (hence inner loops written in ASM)

One way forward is to use multiple processors (eg several Desk tops with Quad processors in a wireless network). This is something I can do but I am interested in other possible routes - hence this question

So, could I run say 100 copies of an inner loop on an FPGA and if so how would this connect to my PC or network? Can I plug some kind of board into a USB Port or is this naive?

I have designed and built electronic devices in the past (about 15 years ago) but nothing involving processors

Many thanks
Bob

You do not build loops in FPGAs.

Loops are replaced by control signals, and registers which are allowed (as dictated by control signals) to update themselves only when a clock signal changes state. If you want repetition controlled by counting, you use a counter to generate the control signals. By configuring counters to respond to control signals, they can be advanced, halted, and reset by other logic components.