The majority of the cards in my cube ended up being from Zendikar block onward (so Zendikar block, Scars block, Innistrad block, Return to Ravnica block plus M11-M13) as that is around the time when I picked up MTG again. For the record I started playing in Revised up to Visions, then stopped. When Onslaught rolled around I started again cause some of my friends started up again. I continued until the end of Lorwyn/Shadowmoor block as I started my teacher program at that time and had no time to play and then when Scars came out I jumped back into the MTG pool as I liked the orginal Mirrodin block and revisiting the place was a cool concept. Anyways, enough about my history of playing MTG.
Building my cube using cards from Zendikar to now does provide some pretty cool interactions despite not having a lot of the older power staples. Zendikar and Innistrad have a lot of vampires so the vampire tribal theme in black is quite well represented in my cube. All the artifacts from Scars provides lots of fixing (and ramp) so the multi-colored cards from Innistrad and Ravnica as well as the giant creatures from Zendikar are easy to cast. There's a bunch of high-quality equipment so creatures are important but at the same time there's plenty of strong removal to keep them in check. Proliferate works great with all the blocks (level counters, +1/+1 counters, -1/-1 counters, poison counters and charge counters all benefit from that mechanic). Another bonus is that, for the most part, all the mechanics are pretty easy to understand. Nothing like Cumulative Upkeep from Ice Age/Coldsnap or Suspend/Vanish from Time Spiral. All in all I think the 4 blocks provide a great starter cube for me and my group.
I figure I will eventually make the cube into a 4 block + 2 core cube which will probably eventually transition into a Type 2 cube (for those folks who don't remember, Type 2 was the old name for Standard). As the sets rotate I will probably dump the old cards into a secondary modern cube (which will most likely be a tribal cube of some form or another as I like creatures and I'm a Timmy at heart)
For those curious, my current cube is here. The yellow cards are cards I haven't physically added to the cube yet but are in my possession.