Most cigalikes are sold with cartomizers, although there are still a few brands like Prosmoke carrying three part e-cig: cartridge, atomizer and battery.
There's a wide range of flavors and various nicotine levels (0 to 24mg or even more) to choose from.
Batteries have the capacity range of 175 - 350 mAh, enough for several hours. Some disposables are even stronger, up to 500 mAh, but I'd never recommend buying them unless in case of vaping emergency.
Btw. it happens that disposables and rechargable cigalikes of the same brand are not of the same quality. So, I honestly don't see the point in buying disposables at all. If you really want to try a brand, buy a small kit. Price range of these is 20-30$.
If you smoke a pack a day or more, with cigalikes you'll need a spare battery to take you through the day.
Batteries appear in three sizes. Most are automatic and some are manual - look at the little button on that one in the pic 2 above. You have to press and hold it while vaping.
About manual batteries: they provide more control over your vaping and get charged fast. Both cig-alike manual batts I have - Eversmoke and South Beach Smoke - take only one hour to get charged. Downside is only that they provide a quarter less puffs on average.
Let's compare the smallest one with a regular cigarette (pic 3 above). Notice that some brands sell cartomizers in two sizes, like Ecigarettedirect from UK. That big one is really a high capacity. It endured almost 9 hours of pretty intensive vaping, so I recommend it for heavy smokers who don't like other, bigger types of e-cigs.
And in the pic 4 below you can see a cutie that I'm vaping right now. It's plugged into my laptop - a USB cigarette. Very handy when you are working on your PCs and laptops - doesn't need recharging.
Now, this can be the problem when you want to combine a battery of one cig-alike with cartomizers of other. There's an overwhelming number of threads but the good news is only few of them are used by most of relevant brands in the market.
GreenSmoke, Eversmoke and South Beach Smoke all have kr808d-2 thread and are compatible, but not 100%. You can vape all of the above brands' cartomizers with GreenSmoke battery, but when you try the other way round - Eversmoke and South Beach Smoke batteries with GreenSmoke cartomizer - you have to make an adjustment - don't screw it on all the way, leave a tiny little space for GreenSmoke carto to "breathe".
Thread 510 is a typical one for eGo batteries. As for cig-alikes you can find it in Panda's Evolve Kit (click the picture below if you want to read our review).
In UK, one of the popular threads is RN4081. Smoker's Angel cigalikes have it as well as NJoy.
This is a link to a fairly reliable compatibility guide by an experienced reviewer. He managed to make something concise enough out of all that threading mess.