One of the best uses of free poker money is to get a start in building your bankroll. There could be no better, risk free way to get a wad of cash together. However, the glory days of free poker cash are long since gone.
Now the only risk free way to get a bankroll together is to try to play your way through the various poker freerolls that are still available at a lot of online poker sites. But be warned - they can be hard going, and a lot of work for very little, if any, reward.
Again, one time, you could find freerolls that had good returns, guaranteed pot sizes regardless of the number of players. So, once the minimum number signed up, you could get a good return in a smallish field.
Of course players caught on to this, and slowly but surely the value disappeared.
There are still free rolls of course, but the size of the field can be enormous, and the pots smallish, and because they are freerolls the play can be a bit maniacal.
But as a way to get started for nothing, they are the only option right now.