This open-label, multi-center study will assess the efficacy and safety of vemurafenib in participants with BRAF V600 mutation-positive cancers (solid tumors and multiple myeloma, except melanoma and papillary thyroid cancer) and for whom vemurafenib is deemed the best treatment option in the opinion of the investigator. Participants will receive twice daily oral doses of 960 mg vemurafenib until disease progression, unacceptable toxicity, or withdrawal of consent. The safety and efficacy of vemurafenib in combination with cetuximab in a subset of participants with colorectal cancer will also be assessed.