> I've seen good things about Africa and Southeast Asia, but I doubt I can get any friends to put up the money to come with me, and I'm not sure I'd like to go there alone with no experience traveling.

Going alone and staying in hostels, you'll find it incredily easy to meet other people.

From December through to January, the weather in South East Asia is fantastic as it's in the cool season (still quite warm). I'd encourage you to grab a flight in and out from Bangkok, and figure out the rest upon arrival.

Australia would also be a great choice at that time of the year.