It's a matter of trial and error, IMO - what suits me may not be the best one for you. I am very sensitive to eye makeup so rarely use it these days, but if I do I tend to use non-allergenic varieties.
I've never found one that doesn't clump. So I've kept an old mascara brush, and I rinse it and run it through my eyelashes after applying mascara and it separates the lashes without removing the mascara.
Maybelline Great Lash in the pink and green tube is great. It's cheap and not blobby, even when you've been using it for ages. Bought a super Max Factor one and it is awful, brush is loaded so sticks your lashes together and your cheeks are covered in black flecks all day.
Boujois = I can't remember the name but it comes in a black and white stripey tube. I never use any other and this never clumps for me. I only ever use one coat though
Don't know if you can still get them, but there used to be tiny combs for eyelashes which helped to separate them when they got all clumpy. I always wipe the mascara brush on a tissue before applying it anyway, that way you can build up a couple of thin layers that way I never have any clumping. Remember too, not to "pump" the brush up and down in the tube
I always use a primer first (like a white undercoat) to separate and add volume. L'Oreal do a good one, after that I think most mascaras are pretty much of a muchness and they all clump as they get older.
The link on that other thread that daffy referred to doesn't work anymore. If I remember rightly it was a link to L'Oreal Million Lashes. I posted on there that I'd try out the waterproof version. I didn't go back to say I thought it was pants! Waterproof versions of popular mascaras quite often have no bearing on the non-waterproof version.
My favourite brand of mascaras has always been Lancome. Quite expensive but good quality. Plus they have a questionnaire on their website so you can find out which of their mascaras will be best for your needs.