My laptop (now 3 years and 3 months old):
CPU: P7350 (Core2Duo, 2.0GhZ per core) - will be upgraded to X9100 (3.06GhZ) in a few weeks,
GPU: 9700m GT GDDR3 - will maybe be upgraded later on to a better one that offers 40% better performance - but I don't think I will in the end.
RAM: 8GB 200pin so-dimm DDR2 - 800MhZ (upgraded today from 4GB),
HDD: Hitachi 500GB 7k500 (7200rpm) - plan to put it into a caddy by taking out my optical drive (which I never use anyway) and place an SSD (80 or 100GB should suffice) as the primary drive for OS and programs - though this upgrade won't happen for another 6 months or more.
That's about it.
I spent about 200EUR for the CPU/RAM upgrade - which I found cheap and better than buying a new laptop altogether (which simply isn't an option right now, and besides, I like tinkering with this one).
I'm thinking the current setup with the new CPU will last me at least another year or two before I upgrade.