I can't find anything else to do in Minecraft?

Trying playing feed the beast mod for minecraft?

My friend and I made an underwater tunnel in survival mode made completely of glass. If you house is near water, it is fun to build an underwater bedroom or room. It takes a LONG time, and helps to have a friend, but you could do it by yourself.

Experiment with redstone…

Well… It's Minecraft. There really isn't much of a set goal beyond that Ender Dragon. That said, I think you're taking the term "survival mode" a little too literally. Surviving on its own is pretty easy. I mean, you can pretty much just dig a 3x1 hole in the ground every night and nomadically go around punching pigs to survive indefinitely. That's not really where the fun comes from.

I'd suggest you focus on building stuff now that you're all settled and established. Make a nice looking house, gather some materials from mining and exploring, and then try building something more ambitious to live in Like a castle or posh mansion or something. And maybe a cool minecart transportation system or something. That's what I usually do.

Make a castle or build a city for your friends to live in. I'm currently building a city and it takes forever! But it really helps pass th time and it's fun too! Explore the land, trade wtih vilagers, fight monsters. Set a new goal every day and achieve it! This is the way to truly enjoy minecraft!

Go for the ender dragon, (defeating it is the the only way to technically beat the game) and build. Part of the fun of the game is the option for building amazing structures, traps, and other crazy stuff. Look up a list of minecraft items, and try making everything. That could be a good goal. Also make a cooler house. Look up furniture making. You could look up mods. There's a lot of cool ones that give you new goals in the games, like the animal one. Find some servers and play with others. I've never run out of things to do in the game, and there's a whole lot of stuff still to do beside having food and weapons. The purpose of those is to keep you safe while you do everything else.