I know what you're thinking: "of course it has, for example, it can be used to tell you how many times you can go around a circle". But that isn't really true, now is it? You'd be dead or the world would go under long before an infinite amount of loops had been reached.
Are there any practical applications for the concept of infinity? Is it a useful concept in maths at all?
I know that Donald E. Knuth has argued that for all practical purposes, a very, very large number has the same effect as infinity, in his book "Things a Computer Scientist Rarely Talks About" (can't remember the exact quote, nor find it online, unfortunately).
Examples are appreciated.
In the BBC's documentary about infinity they interviewed Doron Zeilberger which is probably the poster boy for "infinity is nonsense" in the world of mathematics.
They show him work with $\infty$ symbols when talking about series and functions. The reason this is a good idea is simple.
To say that something is infinite we just need to say that it has more elements than any finite number. But to say that something is finite we need to bound it somehow, which we cannot say in a simple way (and simple way means that for infinite we have a simple schema saying "more than $n$ distinct objects", whereas there is no particular schema catching all forms of finiteness).
In particular this is useful when talking about very small or very large things, it allows us to calculate limits (which is an essentially infinitary process) but discard most of the computation as a remainder which does not affect the outcome, which will follow by taking some error margin.