For keeping track of seeds (especially those of you who type in random numbers or pound the keyboard), I recommend naming your world the same as your seed. This will help you remember which seed is which level. Also, for those who cannot remember or want to find your seed, use http://mc.42nex.us/ as mentioned in the OP.
As for seeds,
mahboi = nothing special (as far as I've seen), but possibly a good beginner world.
AndroidAR = an icy wasteland (my favorite!) that luckily has some trees nearby.
I spawned on X=0,Z=0, and facing south:
To the northwest, there is a nearby terrain spike, and past that, in the distance, is a large, almost squarish mountain that punctuates the landscape. Beyond it is more hills, and next to it is a temperate microclimate surrounded by the frozen tundra: