Best site for ROMs is rom-world.com. The server can be slow at times due to heavy traffic but the site does have almost every ROM you can find for free. And also has the emulators aswell to download.

I also store ROMs on my FTP if you wish to download them then you will need an account.

I think ROMs are fantastic, they bring back memories and good times you had when you were younger. Games like Sonic on the Master System for example .. fantastic in it's day and still one that will get you hooked.