There are many ways that somebody could go and promote their small band. Though Facebook is the biggest option out there for connecting with fans and there are numerous services where you can get more Facebook likes, other options such as Twitter and Instagram are also exceedingly popular. And don't forget social networks that are more specifically geared around music such as Soundcloud which has a very active community. Even MySpace is a legitimate option that has become more geared towards music in recent years.
Beyond just simple raw advertising, there are many other services and providers that provide services that are useful to bands and musicians getting the word out there indirectly. If you're not the graphic designer type, services such as Crowdspring can help you get a big audience helping you with your logo or designs. Or an even cheaper alternative is Fiverr, where many of the basic services will cost you a little more than a cup of coffee. Even though the legal aspect is one of the least fun aspects of making music, it's still pretty important. Having valid UPC and ISRC codes can help and there are services that let you buy cheap ISRC codes in bulk that let you get back to the fun stuff quicker. If you've got a boatload of band merchandise to get to your fans, an online store such as Shopify might be a good option as well.
These are just some of the services that are out there, and this is just scratching the surface of the numerous options that are out there. Unless you have a big music label at your disposal that will take care of this kind of stuff for you, the indie musician still has to hustle and find services that solves some of their problems for them. The key thing is to always look for reviews, do your research, and make sure you're dealing with somebody legit.