Harajuku out on weekdays?

I got the information from my friend that harajuku will gather on every sunday at Yoyogi park. Unfortunately on my trip on sunday i will not in tokyo.
Where can i see harajuku on weekdays?

"Harajuku" is actually the name of a district of Tokyo.

Do you mean the cosplay girls maybe? A few of them still gather on the bridge by the entrance to Meiji shrine on Sundays but not many any more.

You will see some people in interesting clothes in Harajuku (especially Takeshita dori) any day, but more on the weekends. They don't usually hang out in Yoyogi park, although you will see other interesting people there on weekends.

Where do the weekend Rockabilly dancers hang out?
How about the lolita girls and goths?

the lolita girls and goths ARE the cos players (cos = short for costume or costumed depending on what one is trying to say)...it was a fad and like everything else it goes downs...but there are still quite a few young girls and guys that wear unusual clothes in Harajuku and Shibuya and ...

Just have a look at the magazines called Fruits and Tune at http://fruits-mg.com/xnew/e/index.html

the Rockabillies meet a Yoyogi Park, near Harajuku, on Sundays.
http://www.loneleeplanet.com/2011/05/the-tokyo-rockabilly-club/ but it might be a hit and miss too.

Actually lolita and goth styles are NOT cosplay.

The people who gather at Jingu bashi in front of Meiji Jingu on Sundays have been steadily declining since 2005. You're likely to find just as many tourists snapping photos as those who are dressed up hanging out.

Your best bet, as mentioned above, is to take a stroll down Takeshita-dori. There are a lot of photographers for magazines and websites that look to take "street snaps," a la FRUiTS (also mentioned above), who tend to be along Omotensando-dori in between the station and Meiji-dori. A lot of people who dress in alternative fashions make sure to make their way by them in the hopes of getting "snapped," by their favorite magazine.

There is a famous shopping building on Meiji-dori called LaForet that houses a number or stores and brands that cater to lolita/goth/punk fashions. If nothing else, you can check out what the shop staff are wearing (you can guarantee they will be decked-out head to toe).

Lolita and goth are sub culture not cosplay, cosplay usually evolves dressing up as a favorite manga or movie character in costume, I was briefly in takeshita dori yesterday and Lolita and goth can be seen in the growled street, just watch out for Nigerian touts praying on poor gaijin ;) keep your head down and keep walking.

you should kind of be aware that the girls there are generally pretty young too, as in under 16 and not exactly "hot models" lol.
Clubs like Tokyo Dark castle if it's still on and midnight mess are good if you want to see the gothy, alt "adult" tokyo subculture.