Major ISPs (internet service providers) in Sweden are Telia, Tele2, Bredbandsbolaget, and Comhem (a cable TV company formerly known as UPC). The first three ISPs provide the fiber connection (up to 100Mbps downstream) as well as ADSL (up to 24Mbps downstream). Comhem provides a broadband service up to 24Mbps downstream via a cable TV socket. There is also another ISP called Ownit specializing in the fiber connection.
To subscribe, visit an ISP’s website with help of someone proficient in Swedish so that you can fill in the online form, all in Swedish. (Calling them up usually ends up with an automated message in Swedish asking you to press 1 for blah blah blah, press 2 for blah blah blah... So it's best avoided.) You need personnumer to place an order. For the fiber connection, the landline phone doesn't need to be activated.
Before comparing different options, it's best to ask your landlord first if you can install the fiber connection. Maybe you cannot. Then also ask if your apartment already has a cable TV socket by Comhem. If so, it is quite straightforward to activate it as a broadband connection with Comhem. In this case, you don't need to activate your landline telephone for the Internet connection.
A modem will be delivered to you when you subscribe to any of these ISPs. If you want to set up a wireless LAN network at home, buy a wireless router at one of those electronics stores on Kungsgatan (click here for details).
Alternatively, buy a “mobilt bredband” kit from any mobile carriers. Plug a USB-modem included in the kit into your laptop, and you can surf the net anywhere in Stockholm with 3.6M bps via mobile phone network (which means you can surf during commuting by T-bana). Monthly prices start from 198 krona. You can easily buy one at The Phone House. You probably need an ID card, although I'm not really sure. The Local reports on 8 August 2008 that the "mobilt bredband" services can be quite slow.