The Big Island of Hawai'i is composed of five volcanoes... Kohala, Mauna Kea, Hualālai, Mauna Loa, and Kilauea.
Hualālai and Mauna Loa are expected to erupt again. Mauna Kea can still be active though there are no current indications. The current active volcano is Kilauea which has been spewing forth lava pretty much nonstop since it began - and is among the worlds most active volcanoes.
Currently lava comes out at the Pu'u 'O'o vent inside the Hawai'i Volcanoes National Park. Depending on conditions the lava is quite often accessible and offers visitors an experience of a lifetime.
Lava flowing from Pu'u 'O'o normally flows through lava tubes towards the ocean 6 miles away. About two miles before the ocean the lava encounters a 1,200 foot cliff which is flows over, and then two to three miles of coastal flats until it pours into the ocean. Often the lava is visible on the Pali (cliff), on the coastal flats, and at the ocean entry.
In the huge Kilauea Summit caldera itself site Halema'uma'u Crater. On March 19, 2008, a vent opened in the crater causing a portion of Crater Rim Drive to be closed. The vent is still open but lava continues to remain below the surface of the vent.
We have much to say about the volcano and the lava - this page lays out the various sections that you can visit.
Be sure to read the section on Cautions and Warnings as it contains very important information about volcano safety.