Westside:  Silver Lake or Long Lake.  I love Silver for sentimental reasons.  It is where I was introduced to bassin'.  It will always get the nod.

Eastside:  Nothin' fills the bill (or livewell) for me as does Potholes.  Not many fisheries recently that can boast the size and numbers that this fine water has put out, especially spring.  I love the scenery, the many different locations you are apt to find fish, the flooded brush.  Damn, it is going to be a long winter. 

As a side note, Smitty's call on the pool above Tri-Cities is a great call.

Silver works for me at any time.  I have better fish in Spring and Fall, but have caught lunkers in the summer at high noon as well. 

As for Potholes, Spring is it.  April to June.  Current in July and August is a good bet.

Kitsap County's Kitsap Lake in May is probably one of the best lakes in Western Washington for really big bass.  Don't expect to catch a lot of fish but do expect to catch at least two or three in excess of 3 pounds.  My biggest so far is seven pounds, 11 ounces -- And, she is proably still swimming around the docks in late April or early May.