Aozora no Namida from Blood+. I've seen around 20 episodes of this anime so far, and while I enjoy it, some things are quickly getting annoying. (If Saya is the strongest character, why doesn't she ever FIGHT?! And why does Hagi always have to get impaled? He's so under-appreciated.) Anyway, I was disappointed when the OP changed, because I think this one fits the show far better than the Hyde song that came after it. :/ (Btw, the best part is Hagi playing the cello and fighting with his cello case.)
Hishoku no Sora from Shakugan no Shana. This anime is all right. I've seen seven episodes now, and though I find the premise very interesting, it hasn't hooked me yet. The OP, however, I've watched more times than I can count.
Falco from The Law of Ueki. I loved the OP from when I first saw it, and I was looking forward to some good shounen, but the first episode disappointed me. I still rewatch the OP now and then, because it's catchy as hell, so maybe I'll become motivated to give it another shot someday.
Unlimited from Samurai 7. Actually, this isn't recent at all and I really liked the anime, but I'm uploading it anyway because the song is great. :D