I've read a good deal about the above. Ideally, the grounds for various
(telephone, cable, power) electrical utilities should all be common; and
the service entries for those sundry services should be located within
15' of each other.

If I ever build a new house, I will take that into account.

However, it's not practical at this time to realize the ideal. What I
have currently is as follows:

The phone drop (two lines) comes in on one side of the house and is
grounded to the water supply line which comes in the front of the house
(about of 20' of wire clamped to the pipe where it comes through the
foundation into the unfinished basement).

The power drop (100 amp 220v single-phase) enters at the back of the
house, about 30' diagonally from the phone service. A ground wire
snakes from the panel (inside a utility porch) around a couple of
corners and through the floor to a ground post of unknown length/depth
in the crawl space beneath the adjacent kitchen...approximately 20 feet
of wire with at least two 90 degree bends.

The cable drop is around 15' feet from the power service entrance, and
grounded to an adjacent outside faucet a couple of feet away (all
plumbing in the house is copper).

Over the years, we've had a good deal of surge and lightning related
damage to devices in the house...most recently a DSL modem.

Would I derive any advantage by driving a new ground post outside,
adjacent to the power drop and to run all the various service grounds to
it (around 15' for cable, 25' or so for phone)?

Alternatively, I could move the telephone ground wire to the existing
power drop ground post (probably using the same 20' wire), and also
extend cable ground to this point. That would give me a 'star'
configuration with all utilities having around 20'-30' of wire from each
drop to ground.

Moving the phone service drop at this time (the ideal) is not practical.

jak