Here is the "best" route to our cottage.  It is the "best" in the sense of (i) fastest, (ii) least traffic and (iii) most scenic, and is based on years of driving to the cottage from Toronto east.  You start from Highway 401 and Meadowvale Road in the east end of Toronto (the Toronto Zoo exit).

This is a link to the route on Google maps:

Google Map of Route


What follows is detailed maps of the route.

Map 0. it the whole route on one page, without much detail.
Toronto-to-Irondale

Map 1. and 2. are the route in two parts.

Toronto to Cavan

Cavan_to_Irondale

Then maps 1a and 1b and maps 2a through 2f detail every turn from one road onto another.

From highway 401 East, exit to Highway 115, (exit #436).  This is a big exit and easy to spot.
Hwy401_to_Hwy115

Then, follow Hwy 115 for about 38Km and exit at County Road 10 to Cavan.  The exit is on the down-slope of a very long hill with a wonderful vista.

hwy115 to county road 10 at Cavan

Follow County Road 10 north about 18.6 km until you get to Emily Provincial Park on your left.  At the end of Emily Provincial Park, you turn left.  This is still "County Road 10", but it is a left turn off the road you are on.  This turn is one you must watch out for.  You continue on for only about 1 km and then turn right.  This is still "County Road 10".
County Road 10 at Emily Provincial Park

Continue on this county road 10 for about 6.1Km until it T's into County Road 17.  Turn right.

County Road 10 to County Road 17

Follow County Road 17 for 23 km as it winds its way to hwy. 36 just before Bobcaygeon.   Turn right onto Hwy 36.
County Road 17 to Hwy 36

Follow 36 for about 4 Km along the edge of Bobcaygeon.  After the Tim Hortons on your left (open 24/7), you come to a 4-way stop.  At this stop, "Highway 36" goes to the left, but you go straight through and continue north.  This road is Hwy 49 (formerly hwy 649, as it is still labeled on some maps.)
Bobcaygeon
  Follow this arrow-straight road for 21.8 km.  You know when you are getting to the end when you finally hit a slight bend in the road, and shortly after it T's into hwy. 121.  Turn right onto hwy. 121.
hwy 49 to hwy 121

Follow 121 for 10km to Kinmount, and then turn from 121 onto Hwy. 45, formerly 503.   The turn is just before the bridge over the Irondale River, and you turn right up a steep hill.  The sign at the turn says "Kawartha Lakes Hwy. 45 East", and then the next sign at the top of the hill says "503 east".  It was called 503 east for over 40 years, and though it's "officially" changed to 45, even some of the highway signs still label it as "503", as do many maps.
Kinmount

kinmount-to-Irondale
Then follow 503 for 16km and turn right onto the Irondale side road.  At this turn, there is a gas station on your left and the gas station has a Bell phone booth close to the road.  The phone booth is lit up at night and serves as a very good marker for finding this turn.  It can be seen from a distance as you come up to the turn. 
Salerno Lake Roads
Immediately after you turn right, you go over a small bridge over the Irondale river (the third time you cross this river..)  Proceed straight on this road for about 500m.  The Irondale Sideroad takes a sharp left turn, and the Salerno Lake road comes off the Irondale road right at this turn, and you make a right onto the Salerno Lake road.  You follow this road over a small bridge, where the road becomes a gravel road.  As you continue along this road, you will see some roads coming off on the left side.  Follow along for 3.8 km, until you get to Salerno Lake Road 3, also marked as "Twist Lane".  There are quite a few cottage signs at this turn-off, so it is fairly easy to spot.  Follow this dirt road for 0.6km, and then it forks.  Take the left fork.  About 300m after this fork is our cottage lane.  It is the 3rd lane after the fork, and will have a wood sign saying "McIntoshs".  Drive down this lane (it is steep but has a concrete base, so don't worry about getting back up) and park at the bottom.  You're there.