Hiya!
Perth sightseeing? let's see....
Fremantle Port (Fremantle Markets best active on weekend mornings)
City of Fremantle
Aruluen Park (Wildflower)
Busselton Jetty (Breath taking seaside scenery, abt 6 hrs drive down south)
Margaret River (Home of WA wines, abt 8 hrs drive down south)
Carousal (equivalent of SG's Vivocity)
Fisherman's Jetty (again only if you are a sea / fishing kinda guy) - nice place for picnic / BBQ though, and oh, there's the visiting sea lion who's always around too!
Sorrento Quay (Nice place for sunset & fish n chips)
Burswood Casino
Wildlife park little bit north of Perth (40mins drive, cant remember the name though)
Monkey Mia (where dolphins come up, close & personal - abt 8 hrs drive up north)
Rottnest Island (take a short cruise over)
The Pinnacles
Swan River (close to perth city - nice skyline)
Subiaco (little off from city centre but Nike's warehouse located here - very Nottingham-like setting)
Northbridge (the chinatown of perth - dance clubs, late night eateries, asian eateries, strip clubs - vietnamese, chinese, hongkongers, aborgines etc hang out here). DO come here for the wonderful chilli mussels (late afternoon / dinner time) at Uncle Joe (or is it Papa Joe) and Corina Apple Strudels... ;p
If you wanna visit vineyards without wanting to drive all the way down to Margaret River (which is south of perth), there's always the northern vineyards (Swan Valley) which are like only 1 to 1.5 hrs north from perth.