Battle Domes; Where you can fight other neopets, against a neofriend or other neopian characters (bazaar, earth faerie, black pteri, etc.)
Neggs; Eggs, basically. Cheap ones are worth a few thousand. Some re really expensive though. They're in Meerca Chase.
Quest; Well, you can get one randomly or you can request one. Randomly such as; fire faerie quest, air faerie. They each give you different stuff, visit the quest page for what you get. Requesting quests are some such as the brain tree quest, esaphagor, illusen. Give you some pretty decent stuff (items) Oh, and for illusen on quest 30, you can get a honey potion. It was worth 600,000 neopoints last time I checked. But that was a long time a go.
Clubs; I thought these were called guilds...? Ok, well, its a club. Search what club/guild you want in the guild area. Such as....puppies. And it will show you some clubs about puppies. You can participate, join one or make your own. It might take some time for people to join, and people mightn't join altogether. If you're good at HTML you'd be good at making a good layout. You can make layouts without knowing HTML but they aren't very attractive. Ask someone to make you something if you like.
Hope these have helped. :)