Unfortunately, if your planet spins fast enough to negate gravity, your planet won't have an atmosphere. The velocity required for a given orbit is inversely proportional to the square root of the radius of that orbit. In other words, the higher up you go the slower you need to go in order to have a circular orbit.
So here we have two possibilities. If the atmosphere is spinning as fast as the planet, instead of gravity counteracting air pressure to give the planet a nice, thick, breathable atmosphere, the atmosphere will spread out and the surface of the planet will be a near-vacuum. If the atmosphere isn't spinning as fast as the planet, it will act as a brake on the planet and slow the planet's spin over time (a shorter timescale than what it takes for life to evolve). Also, when the atmosphere isn't moving as fast as the planet you've got a devastating global windstorm - Randall Munroe explored the idea in the first chapter of his "What If" book.
So what does life on such a planet look like? Either it is something that lives easily in the vacuum of space, or there's an unobtainum bubble around the planet keeping its atmosphere in, in which case life looks like whatever the advanced civilization that put the bubble there wants it to look like.
How fast does the planet actually spin?
Note that this was the original intro to my answer. I realized that this isn't actually that important for the atmosphere problem, so I'm moving it below the actual answer.
The two biggest formulas to worry about are gravity $F=G\frac{m_1m_2}{r^2}$ and centripetal force $F=\frac{mv^2}{r}$. Another way to describe your planet is that the force of gravity provides exactly the centripetal force and no more. That means we can simplify the equation to get $Gm_2=rv^2$.
Now let's assume this planet is a rocky planet. Using the average density of the Earth (5510kg/m3) and the volume of a sphere ($\frac{4}{3}\pi r^3$) we get $m=23080r^3$. Using that in the above equation, we get $\frac{r}{v}\approx 800$. So for every 800 meters of radius, the required velocity increases by 1 meter per second. Because circumference is proportional to the radius, a planet of this density will have a day that is $2\pi*800=5026$ seconds long, regardless of how large the planet is.