It sounds that BART goes on strike on a regular basis and might be just on the week I will be in SF. What other alternatives do I have to travel between the SFO airport, San Francisco and Oakland. I will be residing in Oakland, so I will be relying on the BART to get into the city. I could take a cab or rent a car but that could be pricy.
The ferry is essentially the only means of transport that wasn't completely overloaded the last time. BART runs a few extra private buses, enough to accommodate 1% of the 400,000 daily riders. And it's only in the commute direction. Unfortunately, the Transbay tube is so efficient and so fast that there aren't a lot of good options from other transit providers.
Perhaps the best option if the ferry isn't convenient is the "slug lines," also known as casual carpooling. People who are traveling solo take on a few extra passengers to get the discount on the Bay Bridge. Obviously, you have to sit in traffic on the bridge, but the price is right. It sounds sketchy but is apparently very safe.
As far as getting to the airport, you're basically out of luck. You can take Caltrain from downtown San Francisco and get off at the Millbrae station. That still leaves you 2.5 miles from the airport, but you should be able to get a cab from there, or walk if you're up for it (the bayfront area by the airport is pretty nice to walk along, but getting there is a slog from the Caltrain station). Also, Caltrain doesn't run as often or as early as BART.
Rental cars aren't cheap, but it may be worth making a refundable reservation in case you need it, and canceling before the deadline if the strike is called off.
The answer naturally depends on where in Oakland you'll be and where in SF you need to get to, but the ferry seems an obvious alternative:
Two terminals in Oakland, and three in more-or-less central SF. $6.25 a pop cash, or $4.75 with a Clipper.
The more boring alternative is buses (see Transit.511.org), which are apparently getting beefed up during the strikes.