I tried Barry M's black crackle ages ago and thought it was great fun but haven't tried any others until now. I found a ridiculously cheap crackle on ebay and thought what the heck! It seems to be by a brand called 'Laushine' and there are dozens of colours to choose from.
Here are the polishes I used. CND in Times Square, Icing (really old!) lilac/clear base with silver glitter and Laushine in pink.
Please excuse the messy application... I took the pics before I cleaned up.
As with most crackles, the thicker you apply the coat, the deeper and fewer the cracks. If you apply the polish thinly you'll get lots of little crackles (like my ring finger on the top photo). I prefer the deep crack look myself, it's slightly less reptilian - I bet green crackle will be flying off the shelves come Halloween for that very reason!
I actually think I'm a little bit over the crackle phase now, but it's a bit of fun! I really wanted to find more of a crack crackle polish like the one below, but Laushine was more of the normal crackle polish you get everywhere. It was a bargain though at £2.46 inc p&p!)