Makalu, the 5th highest mountain in the world at 8,462 metres, is located in the Nepalese Himalayas, 22km east of Mount Everest on the Tibetan border. The origins of the name seem somewhat unclear - Google returns many pages stating that Makalu is a corruption of the Sanskrit name Mahakala, or "Big Black", which is one of the names of Shiva. Most of these pages seem to be quoting or referencing each other, and the word "probably" is used on the most authoritative page (SummitPost), so the exact derivation of the word may be unknown. However, considering the association of Shiva with many great mountains by Hindus, it does seem to be a plausible explanation. In the local dialect the mountain is also called Kumba Karna, the Giant.
Topographically speaking, Makalu has similar features to K2, and like K2 is considered one of the most difficult mountains to climb. It has a four-sided pyramidal shape, with sharp ridges exposed to the elements. Unlike K2, it also has two important subsidiary peaks - Kangchungtse (7,678 m) and Chomo Lonzo (7,804 m). The summit ridge between the main summit and Chomo Lonzo marks the exact border between Nepal and Tibet.
Only 5 of the first 16 attempts on Makalu's main summit were successful. The first (failed) attempt was by William Siri in 1954, who attempted to climb via the southeast ridge and was forced to turn back at 7,100 m by unceasing storms. It was first summited on May 15, 1955 by Lionel Terray and Jean Couzay, who established the standard route followed to this day: ascending the North Face and following the northeast ridge between Makalu and Kangchungtse. There are several more difficult routes possible, but the final attack on the summit pyramid always involves technical rock climbing. The most difficult route appears to be the West Face - after several failed attempts by other teams, this was finally completed by a team from Russia in 1997.
Like K2, Makalu has never been climbed in winter, the only 8000m peak in Nepal for which this is the case. There have been deaths among those attempting it, including that of Jean-Christophe Lafaille, an extremely skilled and daring French mountaineer perhaps best-known for his solo descent of the south face of Annapurna with a broken arm, after his companion had been killed. Jean-Christophe was in the process of attempting to climb all the 8000-metre peaks in the world, and only had Everest, Kangchenjunga and Makalu left. He made the attempt on Makalu solo and in winter, a brave move which fit in with his personal mountaineering philosophy but which was regarded as suicidal by many experienced climbers. His last human contact was with his wife by satellite phone at 7000 metres, when he told her that he was making his push for the summit. His body was never found.
The main reason for Makalu's difficulty is the same as for its Pakistani cousin - its long, exposed ridges leave climbers vulnerable to the weather to a far greater degree than many other mountains. So far 206 successful ascents have been made, with a total of 22 deaths. The only person known to have summited the mountain twice is Sherpa Lhakpa Dorje, who completed his second ascent in 2001.
Makalu is located in, and along with the Barun Valley gives its name to, the Makalu-Barun National Park and Conservation Area. This is a 2,330 sq.km. area of mountains and river gorges, operated by the Nepalese government in a similar manner to the Annapurna Conservation Area Project. Trekking is permitted but is more difficult than around the area of Annapurna due to more extreme terrain and weather (this is the only conservation area in the world with an elevation gain of 8000 metres).
Makalu (Wikipedia): http://en.wikipedia.org/wiki/Makalu
Makalu (SummitPost): http://www.summitpost.org/mountain/rock/150293/makalu.html
Jean-Christophe Lafaille (Wikipedia): http://en.wikipedia.org/wiki/Jean-Christophe_Lafaille
Makalu-Barun National Park and Conservation Area (official site): http://www.dnpwc.gov.np/national-parks-makalu.asp