I saw a lot of these last year in Provinssirock (rock festival):
Flogging Molly (US), MUCC (JPN), Chimaira (US), Aiden (US), Tori Amos (US), Animal Alpha (NOR), Patti Smith and Band (US),
Velvet Revolver (US), Hatebreed (US), The Go! Team (UK), Scissor Sisters (US), The Blood Brothers (US), Lamb of God (US), Oh No Ono (DK), As I Lay Dying (US), Lauri Tähkä & Elonkerjuu, YUP, Julia´s Window, Underwater Sleeping Society, Stalingrad Cowgirls, Sturm und Drang, Smokesuit, Maj Karma, Kotiteollisuus, The Odorants, Regina, Von Hertzen Brothers, Don Johnson Big Band, Disco Ensemble, Empire Fails, Jermaine, Cosmobile, Sydän, sydän, Micragirls, Lovex, Swallow the Sun, Lapko, Mokoma, The Crash, Zen Café, Apulanta, PMMP, Puolustusvoimien Varusmiessoittokunta feat. Niko Ahvonen, Risto, Bloodpit, Nicole, Fat Beat Sound System, Jonna Tervomaa, The 69 Eyes, Superchrist, Jolly Jumpers, Vihreä Maa, The Valkyrians, Grand Slam, Magenta Skycode, Rubik, Sara, I Was a Teenage Satan Worshipper
Not everyone because most of them were crap
I've also seen:
Asia
Uriah Heep
Dio
The Winyls
Hanoi Rocks
Mikko Alatalo
plus some smaller bands I can't remember...
Artists that I will see later this year:
Tommy Emmanuel
KISS
(at least) Foo Fighters (in Provinssirock '08, they are not sure about other performers yet

)
Deep Purple
Santana
Rush