A good place to start is HealthCare.gov. This is the health insurance exchange created by the The Patient Protection and Affordable Care Act, and is a one-stop shop for private individual market health insurance plans (note that the exchange itself is run by the government, but the health plans for sale in the exchange are all private, from the health insurance companies with which you're already familiar). People in 39 states use HealthCare.gov to enroll in individual market plans. The other 11 states and the District of Columbia have state-run exchanges, and you'll be directed to their sites from HealthCare.gov when you select your state.
There are other plans available year-round that are not individual major medical coverage. Most of these plans are not recommended as stand-alone coverage (with the exception of short-term plans, which can be adequate stand-alone coverage if you're healthy and you know that you need the coverage for only a short time; they are usually not at all adequate for longer-term coverage). These plans are not regulated by the Affordable Care Act, which means they can exclude pre-existing conditions, impose dollar caps on your coverage, and don't have to cover the ACA's essential health benefits. In most cases, these plans cannot really be compared with an employer-sponsored plan, since the coverage will be so much lower quality. If an insurance offer sounds too good to be true, read the fine print carefully. It may end up being a poor substitute for real health insurance, and you don't want to learn those details after you have a major claim.
Humana group medical plans are offered by Humana Medical Plan, Inc., Humana Employers Health Plan of Georgia, Inc., Humana Health Plan, Inc., Humana Health Benefit Plan of Louisiana, Inc., Humana Health Plan of Ohio, Inc., Humana Health Plans of Puerto Rico, Inc. License # 00235-0008, Humana Wisconsin Health Organization Insurance Corporation, or Humana Health Plan of Texas, Inc., or insured by Humana Health Insurance Company of Florida, Inc., Humana Health Plan, Inc., Humana Health Benefit Plan of Louisiana, Inc., Humana Insurance Company, Humana Insurance Company of Kentucky, or Humana Insurance of Puerto Rico, Inc. License # 00187-0009, or administered by Humana Insurance Company or Humana Health Plan, Inc. For Arizona residents, plans are offered by Humana Health Plan, Inc. or insured by Humana Insurance Company. Administered by Humana Insurance Company.
Medi-Cal is California's Medicaid program. This is a public health insurance program which provides needed health care services for low-income individuals including families with children, seniors, persons with disabilities, foster care, pregnant women, and low income people with specific diseases such as tuberculosis, breast cancer, or HIV/AIDS. Medi-Cal is financed equally by the state and federal government.