Just a small note but I thought I best mention it as not everyone realises this.
Your /sdcard can often have a lot of garbage in it that you do not necessarily want to appear in your Media Album.
A solution to this is to add .nomedia (a zero byte file) to the directories that you do not want the Media Scanner to scan. What you need to be aware of is that the Media Scanner will skip this whole directory and will not recurse into subfolders. The result being if you drop the file /sdcard/.nomedia then nothing on the SD card will be scanned nor added to the Media Library.
If you're one of those people who drops everything on /sdcard then you need to tidy it up a bit. /sdcard/downloads for example is nearly always the best place to drop your downloads, and you rarely want that stuff scanned. If you do then create new directories:
This way you can simply touch /sdcard/Porn/.nomedia so that it doesn't appear in your Media Album.