How can I combine unpartitioned spaces on the HD? I think the only partition editor I have is GParted, and it's not giving me such an option. There is a resize/move option, but it's always unavailable.

If they're contiguous, then presumably they are combined If they're not contiguous, you will have to move whatever partition is between them. Only way I know to move a partition is (1) copy the data somewhere else (backup or dd etc.) (2) delete the partition (3) remake the partition somewhere else.

If you want to combine two partitions into one large partition and can't move/repartition whatever's separating them, there's always LVM. I.e. you could create partitions in the two unpartitioned spaces then join them with LVM. I'd recommend repartitioning though...

They probably aren't available because you are using the partitions. Maybe you can unmount the offending partitions, but I always find it handy to have the GParted or similar (Parted Magic is good) liveCD available anyway, and you can find links for download at www.distrowatch.com, and then you can simply boot that up and move things around at will

Parted Magic will be the best. Naturally it takes a lot of time to move partitions. But you can do other things while it moves them.