Videos/Movies filling up my HDD
When you delete something in iPhoto it goes to iPhoto's trash. Then from there it goes to the OS X trash. So you need to empty both of those trashes to reclaim the drive space.

Also, I use DaisyDisk to see where I have the most space being taken up. They have a free trial, but you will find it invaluable for freeing up drive space.

Something I use to move videos from iPhoto to external storage is the iPhoto Manager. It will copy the actual event from iPhoto do a different iPhoto library. In my case I have different libraries on different external drives. So I sync everything to the library on my internal drive. From there I can edit, share, etc. Then later I hook up the external drives and copy the events to the correct drives, then delete them from the internal library.