How can I light up a room without a ceiling light?
Usually in this situation, people tend to use lamps. There are two common types of lamps, each available in various styles to fit your tastes.
Floor lamps
These are meant to stand on the floor, and are typically tall.

Table Lamps
These are meant to sit on a table, and are typically short.

Both types of lamps are typically powered through a cord and plug, and have some form of on/off switch built in.
If long range control of the lamp is desirable, The Clapper can be installed.