is this a half post maybe?

Everyone moved from through-hole to surface-mount components.
They're the same components (resistors, capacitors, diodes, transistors & integrated circuits), they just look different.
Overall component count decreased over time too due to integrated circuits doing more and needing fewer support components.

http://en.wikipedia.org/wiki/Surface-mount_technology

Regarding the barrels with strips see http://en.wikipedia.org/wiki/Electronic_color_code.

bristlehog wrote:

[...]
Some barrels covered with strips, named Rxx - resistors maybe?

correct, these are resistors

bristlehog wrote:

Long rectangles (combs?) standing on their edges with many pins sticking into PCB (named RP1 on first image and IC35 on second) - what are they?

resistors again

bristlehog wrote:

Some 'leafs' standing on two legs, named Cxx - capacitors maybe?

ceramic capacitors

bristlehog wrote:

Weird orange drops standing on two legs, named DCx - what's that?

tantalum capacitors

bristlehog wrote:

Black barrels with one side cut, standing on three legs and named Qx - ???

transistors

bristlehog wrote:

At some point all this crap disappeared from PCBs. For instance, SB Pro 2 (CT16xx) has nothing alike, while SB Pro (CT1330) is still covered with them. What was the reason for these components to become obsolete?

like bjt said, the packaging of components changed but they are still the same... capacitors/resistors/transistors/etc

It's really intereting stuff I think. As a kid I spent many happy hours with my cousin who had an electronics kit, allowing us to make simple things that went beep or flashed an LED. My father taught me how to solder and I've done countless simple jobs over the years, so my bareing wires and soldering skills are passable, but I'd love to be able to do complicated things. I'm really impressed with people who have enough know-how to recap a PSU for example, or determine which components need to be replaced on a sound card and do the work themselves.

Just one of the many reasons I like playing around with old hardware; there's always something new to learn!