There are plenty of ferry connections between Åland and mainland Sweden and Finland. Primarily for tax reasons, ferries plying between Helsinki and Stockholm all stop off at Mariehamn or the nearby 30km east, approximately jetty of Långnäs, making this the easiest and cheapest way to get in although docking often happens at inconvenient times in the middle of the night - the Långnäs stops. Mariehamn also has a small airport that serves flights to mainland Finland and Sweden.
MHQ (http://www.finavia.fi/fly...) - the only airport on the islands. There are daily flights from Helsinki and Turku and international flights to/from Stockholm. The flight from Helsinki is less than an hour and the flight from Turku and Stockholm is only half an hour. Mariehamn airport is situated less than 3km north of Mariehamn.
Ferries From Mainland Finland
From Vuosnainen Kustavi, Finland to Åva Brändö by Ålandstrafiken (http://www.alandstrafiken...)
From Galtby Korpo, Finland to Kökar by Ålandstrafiken (http://www.alandstrafiken...)
From Nåtö Houtskär, Finland or Själö Iniö, Finland to Torsholma Brändö by Ferryway (http://www.ferryway.fi/7)
Ålandstrafiken ferries are free to pedestrians and to motorists between the smaller islands. For pedestrians bus lines 4 and 5 from Mariehamn go respectively to Hummelvik and Långnäs, each of which is a terminal for a route to the Finnish mainland.
Ferries From Estonia
From Tallinn to Mariehamn by Tallink (http://www.tallinksilja.c...)
Ferries From Sweden
From Grisslehamn Greater Stockholm, Sweden to Eckerö Åland by Eckerölinjen (http://www.eckerolinjen.f...) local bus: Take the 676 bus from Tekniska Högskolan to Norrtälje and change to line 637 to Grisslehamn. Tickets can be bought at SL Centres or at local kiosks, but NOT onboard.By dedicated bus. Alternatively, Eckerö Linjen's buses to Grisslehamn depart from StockholmCityterminalen 2h 15min before ship´s departure, and from UppsalaHjalmar Brantingsgatan 2h before ship´s departure. The buses returns to Stockholm/Uppsala at the ship´s arrival. The Bus+Ferry Combined Ticket can be bought in CityterminalenStockholm, from the bus driver or at the ferry terminal. Note however that the local buses are a lot cheaper and more efficient, and the dedicated buses should be avoided.
It takes two hours from Grisslehamn to Eckerö. From there the line 1 bus connects to Mariehamn.
From Kapellskär Greater Stockholm, Sweden to Mariehamn Åland by Viking Line (http://www.sales.vikingli...) local bus: Take the 676 bus from Tekniska högskolan to Norrtälje and change to line 631 or 631X to Kapellskär. Tickets can be bought at SL Centres or at local kiosks, but NOT onboard.By dedicated bus: Alternatively Viking Line's buses to Kapellskär departures from Stockholm]Cityterminalen 1h 50min before ship´s departure, and from UppsalaHjalmar Brantinggatan 1h 45min before ship´s departure. The buses returns to Stockholm/Uppsala at the ship´s arrival. The bus tickets must be bought in advance. Note however that the local buses are a lot cheaper and more efficient, and the dedicated buses should be avoided. However, Viking Line often have specific offers for free bus journey between Kapellskär and Stockholm/Uppsala when purchasing a ferry ticket. Look out for the offers on their website!
It takes two hours from Kapellskär to Mariehamn. This is by far the fastest route between Stockholm and Mariehamn, unless flying.
NOTE: If you wish to travel with Viking Line Rosella between Kapellskär to Mariehamn, you should avoid using the international Viking Line website and instead use the website. Become a Viking Club member which is free and not subject to conditions and you can travel FOR FREE Kapellskär-Mariehamn. The prices differ a great deal between international bookings and bookings from domestic websites. For example, the price of one-way ticket from Kapellskär to Mariehamn from the international website is greater than a return ticket which includes bus journey.
From Stockholm to Mariehamn by Birka Cruises (http://www.birkaline.com/)