Bogleheads, inspired by Jack Bogle, founder of Vanguard, leans towards topics of investing, having lots of money, and being able to afford the things you want. If you visit the forums, expect to be encouraged to amass a very large fortune to be able to handle anything.

MrMoneyMustache.com has an environmental slant, and tends to attract relatively high earners like software developers, with the message that you don't need to spend every last dollar to find happiness, and some careful allocation of your money can greatly decrease your working career and open up other possibilities for you (while lessening your impact on the planet.) There's a focus on being flexible and resilient, and many people expect to get their annual expenses in the $30k-100k range, trusting the 4% safe withdrawal rate, and thus having an investable net worth of $750k-$2.5m.

EarlyRetirementExtreme.com is geared towards someone who wants to be very self-reliant and capable, massively decreasing your expenses by decreasing consumption and paying for services you could handle yourself. Here the expectation might be that you could live on as little as $10-25k annually.