I noticed in your posting on port wine that you don't want to bother with the weighing out of small amounts of unknown herbs to make Vermouth -- you don't have to. All Vermouth is is a slightly oxidized wine with some bitter herbs in it.
To start, make yourself a fairly uninteresting red wine and sweeten it (for the Italian style) or get a dry white (for the French style). Once you have done that, go to a homebrew/winemaking shop. They usually have a bunch of flavor essences for making liqueurs -- Vermouth included. Just follow the essence's directions. For the true do-it-yourselfer, just grab the spice rack!
The most common herbs in Vermouth are also common cooking herbs: cloves, cinnamon, aniseed, star anise, citrus peel, ginger, coriander, sage (good for it's bitterness), chamomile (you can get that one from an herbal tea), juniper berries, and hops (one friend of mine has made a collection of Vermouths using only one type of hop in each -- but he doesn't boil them to preserve the aroma). From the garden you can get rose petals and raspberries.
Combine the dry herbs (a teaspoon of each to start), smell them, then make adjustments according to taste. If you only have some of the herbs, don't worry -- you don't need them all. In fact, you should just select the ones you like the flavor of.
Once you have a dry herb blend that you like, put it in a saucepan and add just enough of the wine to cover the herbs. Put the lid on and simmer for 5 to 10 minutes on a low heat. Using the wine instead of water will get the slightly oxidized flavor without risk of ruining all the wine. Let this mess cool overnight (covered) and then strain the herbs out of the liquid, which is now a Vermouth-flavored essence. Just add the essence to the wine until you get the taste intensity you want. Adding a splash of brandy (about 60-ml per 750-ml bottle) is all you need to fortify it.
If one herb doesn't come out as strong as you want, simmer that herb alone in some of the wine, then add it back. Sometimes a touch of oak from some chips adds a nice flavor, too. If allowed to age, the herbal flavor will mellow with time, so if you make it too strong just wait or dilute with some more of the plain wine base.
From the reading I've done, Vermouth was a speciality of monks in France and Italy. They made table wine to sell, and the profit went to the local charities. But, since they did the work in Gods' name, it had to be perfect -- if a wine started to go funny, they hit it with a bunch of herbs to help preserve it. The result was Vermouth, which they would then sell to nearby military garrisons where it was used as an anti-malarial (their version had quinine in it). Today it is an aperitif.
That's all there is to making Vermouth. Not so tough, is it?
My thanks to "Jack" for these instructions.