From the Middle Ages until the end of the Cold War in the 1990s, the Swedish military has had troops, ships and fortifications in the archipelago, for the defense of Stockholm. Today, most facilities are closed down.
The local population relied on subsistence fishing and farming, isolated from Stockholm's enormous economic progress in the 19th century. During the 20th century, many islands were de-populated, and transformed to summer resorts, with very small population during winter. Today, most island-dwellers commute to Stockholm for work, and enjoy maritime life as a hobby.
Värmdö (archaic spelling Wermdö) is the largest island in the archipelago, accessible by road. Big enough to resemble the mainland, it contains suburban neighborhoods as well as deep forests, lakes and beaches. Gustavsberg is the main town. Stavsnäs is the main ferry terminal for the southern archipelago.
Vaxholm (archaic spelling Waxholm) is a quaint, road-accessible island-town, with some shopping, and a major boat terminal.
Sandhamn is a resort island in the outer archipelago.
Grinda is a small rural island, near Stockholm and Vaxholm.
Utö is an outer-archipelago idyllic island with a closed-down silver mine, and remains from the mining industry.
Buses to the northern archipelago depart from Tekniska Högskolan. Buses to Värmdö depart from Slussen. Suburban trains to the southern archipelago (involving feeder local buses) depart from Stockholm Central Station. http://sl.se/Visitor/Plan-your-journey/
Most of the large islands can be reached by car, at some locations through free-ride car ferries. http://www.trafikverket.se/Farja/Farjeleder/Farjeleder-i-ditt-lan/Farjeleder-i-Stockholm213/
However, for a good view, take a boat from central Stockholm, see below.
The Baltic Sea ferries offer an elevated, comfortable view of the archipelago, though without the opportunity to set foot on any of them.
From April through September numerous services operate directly from central Stockholm to various destinations. The major shipping companies are the public-transport Waxholmsbolaget  and the private-owned Strömma (which operates the Cinderella  boat series).
Waxholmsbolaget departs from Strömkajen right downhill T Kungsträdgården, and Cinderellabåtarna departs from Nybrokajen, 400 m from T Östermalmstorg or T Kungsträdgården. Other (and basically the only ones during winter) routes operate from suburban mainland jetties connected to the city centre by suburban rail and bus. Vaxholm, reached by bus 670 from T Tekniska högskolan, and Stavsnäs, reached by bus 433 or 434 from T Slussen are examples of this. Also note that even during the summer, when countless services operate from the city centre it is still, generally, a lot faster to travel via a suburban jetty, not to mention a lot cheaper. This is because even though the archipelago is within the metropolitan area, local transport tickets are not valid, and tickets are paid on a distance basis. However, if you're doing multiple trips, it is also possible to buy a 5 or 30 day card (420 SEK and 750 SEK respectively), which belong to Waxholmsbolaget but are also valid on Cinderellabåtarna.
Destinations in the archipelago include (but are far from limited to) Grinda, Svartsö, Finnhamn, Möja, Sandhamn, Ingmarsö, Runmarö, Nämdö and Utö. From April through september most of these can be reached either from the city centre or via suburban jetties. The islands offer a wide variety of nature, from the lush green of the inner archipelago to the bare cliffs of the more distant outposts. Some islands have restaurants, youth hostels and country stores, while others are entirely deserted islands.
A good destination for a day trip is Sandhamn, which is reached either by taking a direct ferry from the city centre (this takes 5 h) or by taking the 433 or 434 bus from the centrally located T Slussen to Stavsnäs and from there a connecting ferry bound for Sandhamn or Hagede (from T Slussen this takes 90-95 min during summer and 110-115 min during winter). Both Waxholmsbolaget and Cinderellabåtarna serve both routes, but again, Cinderellabåtarna service is shut down during winter.
Utö makes another good trip and is accessible from the city centre (takes 3.5 h) or by taking suburban train from Stockholm central station to Västerhaninge, then bus 846 to Årsta brygga and then a connecting ferry (from Stockholm C this takes 90 min during summer and 1 h 45 min during winter). Both routes are served solely by Waxholmsbolaget.
In general, the further out to the ocean, the more spectacular the view. During summer, sailboats add to the scenery. Among peculiarities to expect, are small islets with a single red cabin, and cormorant colonies.
Outdoor bathing and hiking. Rod fishing is allowed without a license, at most locations.
Unfortunately, Stockholm currently has no domestic seafood market.
Most boats in regular traffic have a simple bar, offering regular beer and wine.
Ticks, fästingar, are common in grassy areas of the archipelago.