Richard from EspressoReport put together a thorough tutorial that will get you up and running with OS X Leopard on a Dell Inspiron. Arguably, it's not the most sexy hardware, but at the $650 list price with dual core performance and the natively supported graphics chip (same as the MacBook's), it's not a shabby alternative to running OS X on Apple hardware.

Under the hood boasts a little bit older processor technology with a 533MHz FSB -- Intel Pentium Dual Core. This is very similar to the new Celeron Dual Cores but don't let it confuse you with the Pentium D -- this CPU is actually rather nice. Although using the Pentium name, the Pentium Dual Core is based on the Core technology you're already familar with on your Core Duo and Core2 Duo Macs. While the battery doesn't last quite as long as a similar Core2 Duo (Centrino), this 1.87GHz packs a punch and unlike all you other dual core users, I don't have to boot with cpus=1 -- that's right! This HackBook Pro is using both cores and it's putting out some power with Mac OS X.

Of course, you'll have to wrangle with the ethics of installing OS X on hardware that Apple doesn't wish you to. Perhaps the thought of ridding an innocent laptop of Vista will provide you with some solace.

Dell Inspiron 1525 HackBook Pro Tutorial

I can't find any documentation for this, nor can I help posting it.

I assume it's a hardware hack that manually controls the floppy drive's stepper motor, but it'd make my day if this was done in software using standard I/O requests. Either way, the 3.5 inch FDD finally serves an important function again.

Star Wars Floppy Disk

For a buck's worth of materials, you can quiet your PC by damping your hard disk's vibration:

As the pictures show, the drive is essentially suspended on the stretched elastic. The resilience of the elastic stops all vibrations from passing from the drive to the case -- or vice versa, for that matter.

...

When I showed one of my suspended drive systems to my favorite local dealer, it was the complete absence of vibration in the case that amazed them the most. They could not tell when the PC was turned on by the usual vibration of the case. They found it eerie.

Keep in mind that you'll loose some of the conductive cooling that you get when the drive is mounted to the case, so it'd be smart to do this in cases where there is decent airflow or find a way to attach some sort of heatsink to the bungeed drive.

Hard Drive Silencing: Sandwiches & Suspensions