Bike repair stand

+1 for the Aldi 'Bikemate' stand. Very solid.  Don't recall it coming with a wall mount though, maybe that's a new addition.

Not currently listed online though, so you'll either need to have a rummage in your local stores or wait for their next cycling 'specialbuy' event (and even then its not guaranteed to be one of the items offered).

Ive got the Aldi one at £25 it was a bargain, 25kg so you could throw it in the back of a car but currently lives in the corner of my living room holding the bike (I live in a flat) it also has a wall mounting system which was pretty cool 

I've got the Elite Spindoctor Essential, picked it up second hand off eBay for about £30.

Not exactly portable, but easy enough to take out the garage and set up in my garden.  Simple to use, solid and stable.  Folds flat when done.  It's basic but does the job very well for me.

Mine's a simple Minoura DS-30AL. It's really a display stand meant to prop up your bike's rear QR skewer. As the wheel is a couple inches off the ground, though, it's very easy to use it for checking your derailleur indexing.

With the use of a wall, I can rotate the bike upward and lean it on the wall by its brake hoods. That enables access to the bottom of the bike and frees the front wheel as well.

When not needed, it folds flat for storage. Not as compact as, say, a Topeak Flash Stand, but very effective.

I've got one by a company called Black Dog. Is great, and wasn't too expensive. I over-torqued a nut on it and cracked the plastic, but it still happily holds my bike up off the ground so I can do stuff.

Two suggestions at different ends of the spectrum.
The topeak flash stand is about £25 quid and is perfect for fitting a rear wheel or sorting out indexing. Sits under the BB and lifts the wheel up enough.
For more major work the Park Tools PCS-10 is solid and stands up to regular bike washing and being bumped around the house, you can also fit the ts-25 wheel truing stand to it, so it's kind of good value...

I have the revolution one from Edinburgh cycles. I picked it up cheap in the sales, a couple of years ago. No complaints so far.

I bought the Lidl one (I think at the beginning of the summer?) and it's great for the price. 30 quid, I think it was - a tiny bit more fiddle than the expensive ones, I suspect, but it does the job very capably. Definitely worth keeping an eye out for it if you can wait. It weighs a lot though.

Not sure if its Aldi or Lidl but both my dad and brother have bought the stand they sell. Its perfect for everyday cleaning and repair jobs.

The only problem is that they dont come up for sale to often.

Depends what you mean by portable.

I have the "Bike Tool Aluminium Workstand" from Ribble which cost me fifty quid. It's light and folds neatly, but I'd be unlikely to stick it in a rucksack and take it on a tour. It's ideal for slinging in the back of the car though.

It's adjustable and strong enough to cope with 99% of maintenance and bike build jobs. I have taken the bike off the workstand to set about sticky bottom brackets, but it's coped with everything else.

I have a Topeak PrepStand Max: http://www.topeak.com/products/repair-stands/prepstandmax

Rather than holding the bike out from one side like some stands (the aforementioned Minoura for example), the bike sits atop the Topeak, with a cradle supporting the downtube before hooking under the bottom bracket, a threaded hook then holds the bike tight against the cradle. This hook can slide up and down the cradle so as to avoid bottle cages or whatever. While this is perhaps a little clunky compared to a clamp, having the weight of the bike push down on the stand actually helps keep things steady.

There's a fair range of height adjustment, lockable with a quick release handle, making it easy to lift or drop the bike up to a comfortable working position. You can also spin it around to get to the other side if need be.

There are grooves in the supporting cradle so that cables aren't squashed up the downtube and have a clear run to the back of the bike. The bottom bracket cable guide on one of my bikes doesn't sit perfectly in the cradle, but this doesn't seem to affect being able to tweak gears.

Although the stand's name alludes to it being for bike preparation, I've used it for multiple full bike builds without issue.

It folds down into a bag similar in size to those folding chairs you see everywhere. Certainly small enough to be left kicking around the back of my car, and definitely small and light enough to be classed as portable.

It's perhaps not as slick or sturdy as a 'proper' workshop stand, but I'd thoroughly recommend it for portable tinkering and more.

I don't think any of them are 'tuck it under your arm' portable, they weigh a lot which is good because it helps stop them falling over. No problem in a car boot or taking it from a flat to a garden though.

I've got a Minoura 1000 which was about £80 and works very well for mechanical work and cleaning the bike.