Open all files in a folder

To edit all files in the current folder, use:

vim *

To edit all files in tabs, use:

vim -p *

To edit all files in horizontally split windows, use:

vim -o *

The other answers will not work if you have subdirectories. If you need to open all files in all subdirectories you can use command substitution:

vim `find . -type f`

If you want to ignore files in subdirectories write:

vim `find . -type f -depth 1`

You can, of course, get as fancy as you want using the find command.

Sounds like you're on linux or some Unix variant. Using the asterisk gets you all files in the current folder:

$ vim *