What's the smallest 8-pin connector available? It's for occasional use but it must be easy to insert/remove whatever cable it would accept.
Is it FFC?
"About 8,460,000 results"
Thanks for narrowing it down for me. 
That's how narrow you're search criteria are... What's small? What currents? Voltages? Hand solder? etc
Fair enough.
3mA, 3.3V. Hand solder.
Size is the question, but no larger than 10x5x5 mm.
Sorry, I thought the criteria you set out was vague.
I am sure if you look at some of the offerings on the page you can come to a decision.
How about 4 by 4 JST or DuPont connector?
Is this cable to cable or cable to chassis?
You can make your own if it is cable to cable.
Get 8 male pins, 8 female pins, solder to wires, heat shrink each pin, then heat shrink the group of 8.
You can polarize the connector by having 1 male and 7 female then 1 female and 7 male.
Okay, it was a dumb question. I don't know what's available and couldn't pick a JST or DuPont connector out of a lineup. I suppose it was like asking how you program an Arduino.
I want to be able to occasionally connect a cable with 8 wires to an AVR that is on a small PCB. It's the connector on the PCB that I want to be of minimum length, width and height. An FFC connector is one possibility but I'm sure there are many others.
I have used 4X4 IDC, JST and DuPont.
These all are a good choice.
.
At the risk of being accused of a thread hijacker 
is there a 1mm pitch connector similar to the DuPont style that can be hand crimped? I tried Element 14 but got lost in the sheer variety available, and all the 1mm stuff seemed to be for pcb mounting whereas I want cable fix.
LarryD:
I have used 4X4 IDC, JST and DuPont.
These all are a good choice.
And you can find these in 10 x 5 x 5 mm size or less?
@dannable: Hijack away.
you could take a look at jst series connectors.
Be aware though that once you go below dupont size the crimps get very fiddly and the required crimp tools get very expensive.
Addendum.
Professional crimp dies can cost 400.
Pololu do a crimp for 40 which is ideal for dupont.
They can be used to do an acceptable crimp on jst though.
Its fiddly precise positioning and two crimping operations are needed.
Measured DuPont.
10mm long, 5mm wide and 15mm long (in the direction of the cable).
The moment you depart from common connectors (like the 0.1" DuPont connectors and 0.1" headers), you start having to work with difficult connectors (the crimp tools are hard to find, expensive, and hard to use), which are expensive, less readily available, and heaven help you if you forget the exact part numbers of the matching connector - You'll never find it again!
It's like the tower of babel, where God cursed man for trying to reach heaven by causing everyone to speak different languages. I don't know what we did to bring the same curse upon us w/regards to connectors, but we must have made Him pretty angry... There are tens or hundreds of thousands of different connector designs, many of which are almost indistinguishable until you try to plug one into the other, and they don't fit. Not only that, confusion about the proper naming scheme abounds - a while back it took me three tries to obtain something to plug into a JST-PHR-2 connector - they all said that's what they were, but they were all different. Several people suggested a "JST" connector - okay, which one? JST is a company, they make connectors ("Japan Solderless Terminal"). They have a huge line of connectors in a great variety of sizes, shapes, and pin counts - So a "JST connector" could be any of the hundreds of connectors they sell. And there are multiple similarly large connector outfits (molex and amp come to mind). There's a huge amount of choice, and as far as I can tell, below 0.1" pin header and dupont jumpers, there's not any particular option that's popular enough to be the "go to" connector.
If you could spare just a wee bit more space, you could fit a 4x2 right angle 0.1" pin header on the edge, and you wouldn't have to worry about maintaining a stockpile of exotic connectors...
tldr: Exotic connectors are nothing but trouble.
If you want 6 or 10 pin and budget is no problem, maybe Tag-Connect? MCU/FPGA/DSP programming cables, adapters, small footprint | Tag-Connect
They are used for programming microcontrollers, so the plug/cable is expensive, but no socket
is needed, just a specific pad/hole layout on the PCB.
Measured DuPont.
10mm long, 5mm wide and 15mm height (in the direction of the cable)
This is dirty but - if the use is really infrequent, you can even use standard 0.1" header holes, and put header into those holes and apply gentle pressure at an angle with your hand to keep it in contact while you program it.
This is how I bootload the boards I sell that don't come with pin header attached.
MarkT:
If you want 6 or 10 pin and budget is no problem, maybe Tag-Connect? MCU/FPGA/DSP programming cables, adapters, small footprint | Tag-ConnectThey are used for programming microcontrollers, so the plug/cable is expensive, but no socket
is needed, just a specific pad/hole layout on the PCB.
Those are pretty cool. I'd only need one but still kind of expensive.