[saq]

And Linux

[Hamuko]

Linux would be the biggest one since most of the Internet is built on top of it nowadays.

[vsipuli]

And Git (kind of, although that happened after Linus moved away from Finland)

[Eyght]

MySQL in the same vein.

[welfare]

MySQL is actually of Swedish origin.

[cfinnberg]

Well, at least Michael Widenius, the most visible head of MySQL and one of two cofounders, is finnish. He also created the MySQL's fork MariaDB. Both names came from Michael's daughters My and Maria.

[marvin]

And if you want a less glamorous tidbit to add to that list, OOP originated in Norway with the SIMULA language in the 60s.

[krebs_liebhaber]

How did I forget about Linux?

[vsipuli]

And SSH