I made a swap partition to install Ubuntu on my MacBook Air 2011, but now I want to clean all the partitions up. However, I can't delete the "swap partition" in Disk Utility. Can anyone help me?
You should be able to use a tool, such as a GParted Live CD, to delete the swap file partition and resize the OS X partition afterwards.
Per this Apple discussion forum that covered this topic:
I believe that you can do it with a Live GParted CD.
Boot with the Live CD in the drive and delete the swap partition. You may even be able to resize the OS X partition with GParted afterwards.
Alternately, back up all of your data and applications and wipe/repartition the main drive and install OS X from scratch. Takes a bit longer, but will give you a fresh OS X installation.
To delete swap partition go to disk utility. Select that partition, and choose erase from top right. From the the format options choose Mac OS Extended (Journaled) and press erase. This will erase everything on that partition. Now go to Apple SSD (or whatever is the hard drive where this partition is), choose partition. In the partition menu on the left hand side there will be all the partitions, choose the swap partition and press the "-" (minus) sign at the bottom. This will delete that partition. Then you can just pull and drag the mac partition to resize it. Hope it helps.