Locking it up...

Have an Oxford cable lock wrapped around the handlebars on my hybrid - if I'm going to be leaving it for very long, I'll double up with a Kryptonite cable carried in a small rucksack.

Commute bike has an Oxford beefy cable lock kept in the works bike sheds.

Other bikes don't get left unattended.

I've thrown away the kid's weedy cable locks and given them all Clas Ohlson D-locks. These have 18mm shackles, are Bike Gold approved and cost £19. It's a beast, and probably stronger than my NewYork lock ... be aware that some ppl in Scandinavia report the lock sometimes won't unlock. My guess is that water gets in the mechanism and corrodes it, so protect from the elements if using it for commuting, and lube as needed. Got 4 of them in use - all fine so far ... they're labelled Asaklitt 31-2166.

I use Kmart cheapies but feeling the weight of the coated chain model off put me a bit so I'm about to try 7 foot 10mm cable instead. Some bikes aren't quick release hence long cable should be fine. I have a padlock to secure cable ends with.
Note: I don't normally leave bike out long. Doesn't look secure. 7 foot allows both wheels and frame a good chance of survival. If any good I'll repurchase 2 4foot10mm cables.
I think their handy. They compliment use of ubolts and their currently about $12 (7 quid)

Always fancied the master lock cuffs as a quick lock.

Otto lock is tempting me. Much like cameras - the best lock is the one you have on you. 

Kryptonite new york chain is the minimum I use and carry.  Never give them a chance.

rarely lock mine up where I live North Herts 29 years and counting). Whilst I'm sure it's an issue in some circumstances and I do assess each time if I'm shopping for a longer period, 85% of the time I don't bother with a lock. I'm usually on the daily anyway so the simple coil lock is in the pannier side compartment anyhow.

I do lock it up at the hospital because it's located in a right pikey town!

If you are just popping into a shop or cafe where your bike is only out of your sight for a few minutes a good quality cable lock is fine. The chances of a thief with some bolt cutters coming along whilst you are away from your bike is tiny.

If I think I am going to stop whilst out riding I wrap an Oxford cable lock round my top tube. It looks untidy, but it makes it easy to carry.

If I am going leave my bike for a while I have an Abus folding lock. It can be mounted on to the frame, but it is very heavy.

I don't leave any of my current bikes unattended, other than at the secure cycle parking where I work. I leave my commute bike there (requires key card access) locked with two Gold secure D locks which I leave in my locker.

Before I sold my pub bike I often left that secured in public with only a silver secure lock and a cable through the wheel (but even then I wouldn't leave it long).

Thieves in Bristol with have anything (my mate had a bike stolen from inside his house, whilst he was at home).

For this sort of thing I'd be on my commuter/hybrid and would, for a few minutes, use the D lock (silver rating) through the seat stays and rear wheel (may well leave the lights fitted).  Anything longer and I'd have the secondary (thick) cable lock on through the frame and front wheel (+ a thin cable from the saddle to the D lock and all lights/speedo removed).  Not worth taking the risk and having the 'nausea' of having your bike nicked (been there).  There's a lot of weight in the locks but 'that's the way it is'.  I know a few people who have 'scrimped' on locks (cost, weight or both) and have paid the price.

Road bike?...pocket sized combo/cable lock, but also have a way of taking a mini-D Lock (2 bits - using seat pack) if, for a reason, I'm locking it up for a while in a town (rarely).

It's horses for courses for me.

If it is left in any area within the city then I use a Sold Secure Gold Oxford lock which weighs a lot but is worth it.
If I am out in rural areas then the simple abus chain (non resetable) combination lock is ample enough for me.

I have changed my quick release skewers for security ones so that they can't easily just take my wheels and come back later. This also helps when having to lock up to poorly designed stands that only allow the wheel to be locked to the stand.

Most of the time I don't lock it, but that's mainly because its got a dirty great tagalong on the back and as such the whole thing weighs around 20 kilos. Also live in a rural area so crime is low.

If I'm leaving it for more than 5 mins out of my sight then I use a big Oxford D-lock (Sold Secure Gold) that does indeed weigh a ton. Not an issue because the bike is so heavy and its in a pannier.

On my best road bike I never leave it unattended so don't have a lock. I'd like one of these, waiting for them to come back in stock in my colour/length.

I would never leave my bike locked up unattended but if I do pop into a shop for something I use one of those ones the police give away. It's a bright green plastic coated self coiling lock that doesn't weigh much. Wouldn't stop any kind of thief but well up to stopping kids wandering off with my bike.