Just today thanks to this answer on SO, I realised that vim can automatically pipe text through a shell command. Just think about that for a second For a simple example you can write python code into a text file, and execute it which replaces the code with the result.
for i in xrange(10): print i
Selecting this text with in visual mode (you should all know how to do this) and typing !python which will get replaced with ','!python since youre in visual mode. This will replace the code written above with the numbers from 0 to 9. This could even then be piped into eg. !sort -r to reverse the list. A use Ive come up with is to pipe code into grep for data file formatting. Let me know any uses you have in the comments.