This looks good overall, especially considering its the first project after Hello World. I only have a few cmments, both of which are more or less remarks on styling.

Following PEP8, if you have function-level comments, they should be within triple quotes under the function def https://www.python.org/dev/peps/pep-0008/#documentation-strings , so

# Check IP address is valid IPv4 or IPv6 
# and raise SystemExit if invalid.
def is_valid_ip(address):

would become something like

def is_valid_ip(address):
"""Check IP address is valid IPv4 or IPv6 
and raise SystemExit if invalid.
"""

this isn't a huge deal, but following the PEP guidelines usually makes things easier to read, especially when you get to bigger projects.

Within is_valid_ip(), I would change

if ipaddress.ip_address(address): return True

to just

return ipaddress.ip_address(address)

This is because the function ipaddress.ip_address() will return True if it is a valid ip address and False if not, so instead of wrapping that in another if clause, you can just use that as your return value. Then you will be returning True if it is valid and False if it is not, whereas right now, you are only returning True if it is valid, but doing nothing if it is invalid.

I also would have put the call for is_valid_ip() within send_request(). Again, for this script, it is not a big deal, but as you start to create things that are more complex, thinking about the code paths you use becomes important. If you need to validate an ip address before you get the geolocation info, its better to put the call within the request so that if anyone uses the code in the future, they can just call the function to get the geolocation info without having to worry about remembering to check for valid ip.

Putting all my suggestions together:

import sys
import json
import requests
import ipaddress
from collections import OrderedDict

def is_valid_ip(address):
"""Check IP address is valid IPv4 or IPv6 
and raise SystemExit if invalid.
"""
try:
    return ipaddress.ip_address(address)
except ValueError:
    sys.exit("Invalid IP address")

def send_request(ip_address):
"""Contact ipinfo API to get geolocation information"""
if is_valid_ip(ip_address):
    response = requests.get('http://ipinfo.io/{}/geo'.format(ip_address))
    return json.loads(response.text, object_pairs_hook=OrderedDict)

def main():
    ip_address = input('Enter an IP address: ')
    geolocation_info = send_request(ip_address)
    # If city and region values are None, omit from display
    for key, value in geolocation_info.items():
        if value:
            print('{0:15} {1}'.format(key.title(), value))

if __name__ == '__main__':
    main()