After removing Bootcamp, my Hard Disk has around 80GB missing I removed Bootcamp earlier via the BootCamp Assistant, and it flashed some error up that I just ignored.

Now, when I've gone back to reinstall Bootcamp, I've noticed that while the disk reads as being 500GB in total, there is around 80GB unaccounted for in the GUID table..?

Here is an output from terminal:

diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            419.2 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3


Any ideas how to get back the missing disk space?

EDIT: Might be worth pointing out, I am running the latest public beta of OSX 10.11
I'm guessing that OS X probably mis-partitioned it when removing the Bootcamp partition, and the old Windows partition is either free space or corrupt. Either way, you can try to go to Disk Utility or boot into Recovery(like @klanomoath said) and check to see how the partitions are setup. You can then resize the Macintosh HD to use any free space, and erase any corrupt or unneeded partitions.