Honestly, I don't think there's any need to "force" yourself to read "shoujo" manga. Just read what you like. That being said I dislike classifying manga that way. Hmm… anyway onto recommendations. Off the top of my head:
Natsume Yuujinchou: You like Mushishi, right? If you don't read it or watch it. Then you will. This is pretty much like Mushishi except more flowery.
Taiyou no Ie: Kind of standard romance with a gender gap (older guy, younger girl if it matters–I prefer the opposite). Very cute without being cringe inducing for the most part. I feel it appeals to guys as well so~
Skip Beat & Ouran High School Host Club: Both are long and drag but for the first 10 volumes? Very much worth reading for the comedy.
3Gatsu no Lion: Technically seinen by the author of Honey and Clover (also recommended–just watch the anime), about a (sorta) prodigious shougi player going through a rut.
Shigatsu wa Kimi no Uso: There's an anime adaptation airing right now. It's good. Go watch it. (It's about music so audio enhances the experience. They're adapting the whole thing.)
Glass Mask: Classic but great. Weird how lots of classics aged well today while more modern works aged terribly.
1/2 Prince: I'm not too fond of it but if you're into the whole MMO craze, it's decent.
Fruits Basket was really popular when I just got into manga. I never did quite see the appeal but it's not bad. I know some girls who swear by it.
There are some 90s shoujo like like HanaKimi (my mind still want to recommend this but it does drag), Mars, Hana Yuri Dango (might as read Cat Street: shorter, similar themes, more modern), etc. Not sure how well they've aged. I mean Dragon Ball (not Z) was good but I wouldn't call it anything more than decent today.
If you're interested in josei too:
Chihayafuru. Technically, it's published in a josei magazine (I think); although, thematically there's no reason why it couldn't have been published in a shoujo magazine (or a seinen magazine for that matter.) It should be an easy transition if you like sports manga. Not to be read for the romance… being Taichi is suffering.
Sakamichi no Apollon: BFF's play jazz. Honestly, don't know why this wasn't published in a seinen magazine. I mean there's bromance but there isn't any bromance. Seems like it'd appeal to guys more. The anime is pretty good and there's music so I'd watch that.
Nodame Cantabile: You've probably already read or watched but if not.
Kuragehime: Has an anime (but I haven't watched it.) The manga is pretty funny. One of the MCs is a crossdresser (male) so if that turns you off stay away. (This doesn't seriously explore that theme in any way, shape, or form.)
Usagi Drop: Watch the anime.
And some more SoL-ish shounen/seinen:
ARIA: About girls rowing boats and discovering the joys of life. A calm and peaceful manga. There's an anime, which is pretty good if you prefer that. I also like Amanchu! by the same author.
Stuff by Sahara Mizu: In particular My Girl. Heartwarming story about a man raising a daughter he didn't know he had.
Yokohama Kaidashi Kikou: About a robot in a post-apocalyptic world running a cafe.
If you want to "expand your horizons" I could recommend some stuff that's pretty bizarre or stuff that explores some uncommon themes and topics. Above was mostly a list of popular stuff. I could also recommend some more niche anime. Stuff like La Maison en Petits Cubes.
This is the prove of someone with good taste in manga .