Do you get Austin Reed in the US? They are very good for work
http://www.austinreed.co.uk/fcp/departmenthome/dept/womens?resetFilters=true
I was going to suggest RM but it's at a high price point.
As is Acquascutum perhaps but you might be able to find some pieces in the sale still.
http://www.aquascutum.co.uk/womens/aw2009/aquascutum-london/
Sorry about the UK theme but Jaeger is also good
http://www.jaeger.co.uk/index.cfm?currentPage=2&page=1472
Sorry about the European bias here, perhaps it will help someone else reading this if not the OP.
You may be surprised how many good work dresses and suits Dolce & Gabbana and McQueen do (but again expensive).
I think it's hard finding good things for work because so many designers chase the same 'ladie's of leisure' market..