Wikipedia is your friend:
Brightness and Candelas
LCD Pixel Response Time
Of course, the most important thing to remember is that manufacturer's stated specifications are often measured inconsistently or grossly exaggerated based on certain technology "tricks" (e.g. dynamic contrast algorithms). Best thing to do is go to Comet, Dixons etc and have a look at a few TVs, side-by-side, making sure you can adjust the settings to your liking.
You in the market for a new TV then?
Opteron firstname.lastname@example.orgGHz (stock HS/fan), Asus A8N-SLI SE (passive NB), 1.5GB RAM (2:3:2:5, 2T), WD Raptor 740GD 74GB, Maxtor DM10 300GB, Asus EN7600GT SILENT@???, M-Audio Revo 7.1, Nebula DigiTV, Dell 2005FPW, Enermax 431W Active.