Building my first really nice base (SP) gave me a new appreciation of those big manicured estates. 

I leveled off a gentle hill to get a 50x50 area (took forever and I don't know how many shovels);
then a 23x23 basement (oh god, so many pickaxes);
and a 15x15 building with (mostly) wood floors and glass walls that's three stories tall so far. 

I thought I had ridiculous amounts of glass (my spawn point is right next to a large sandy area).  I was wrong; or more precisely, the building required even more ridiculous amounts of glass. 

I thought I had stupid amounts of coal and torches and sufficient amouts of wood; but when my supplies started dwindling at an alarming rate I decided to use my large "lawn" to farm trees.  Cue charcoal production. 

I will post pics if I get around to uploading them. 

Notable encounters:  LAVA SQUID!!!
(An underground stream beached about 4 of them right next to a lava lake)

and UNDERGROUND REEDS aka sugar cane
(Apparently they don't need light to grow)

I know how you feel.  I dig what feels like a long time in my mine, and feel like I make some really nice progress.  Then I go up to my 8x8 tower and add...

...two, maybe three stories.  So unsatisfying.  I think I need to make my stories taller.  It should use less resources that way.

I make my stories each anywhere from four blocks per (including the floors) to seven blocks per, depending on how majestic I want them to look.

Anyhow, here's most of the stuff I've built. I tend to go for things that are incredibly grandiose, then they get so big that I never quite get around to completely finishing them. Meh.

My original castle. This thing is completely, 100% constructed, but I never got around to completely furnishing it. This pic also shows some of my pixel art.

Most of the rest of my pixel art. Also shows my very first building ever, and the glass bridge leading to my first "pre-planned" tower (not shown).
The bridge shown in the background is part of my network of bridge-roads I'm building at the moment to connect all of my creations by road.

My second castle. I consider this one more of a prison than anything else... at least, that's what it looks like. Notice the bridge on the right side? This's also connected.

My latest castle. This one's by far the most beautiful and complicated. It's smaller than the second one, but it has a lot more going on. There are bridges and balconies and hallways all over the place, as well as a full castle-town inside the main outer walls (which are what you're seeing here). There's also a full fountain system, which makes it really pretty too.

Here you can see most of the castle town and the main fountain-tower.

This shows the inner castle up close, as well as the front of the church and, opposite that, the minecart station.

Inside the church. Piano, keyboard, pulpit, baptismal, sound system, communion table, and seating space for 157.

Edit: Oh, BTW. These were taken while I was using my custom texture pack, The Cel-Pak. For those interested, you can pick it up here: http://cl.ly/49aP

No...words...

I... like to build.

How did you get all the raw material?

For the most part, just a whole lot of tedious, creative mining.

Right now, I'm working on building my first major non-castle-related building since I started the first castle (the hilltop one). It's going to be a seaside mansion with two balconies, a dock, a very large wooden dining table, and a fireplace, among other things.

Since it's wooden with carpeting, it's highly flammable, so I expect to burn it down once or twice before I master the whole fireplace thing. This is why I'm using MC Edit to make a backup of the construction before I introduce the fire to the fireplace. If it burns down, I can just essentially reset it to before I put the fire in and I won't have hours upon hours of construction lost.

I intend to make a recording of it when I do that. Y'all might enjoy seeing my mansion burn down. ;D

This post made me go "WAIT WHAT" and then I looked back and saw that you were not as I had assumed in Classic mode where you get to place blocks for free and get to mine instantly.  And not die when you fall off one of your creations mid-construction. 

Now my mind is blown.