Um, not sure if this is something new or has been posted already but I used to follow the following steps to start hammer:

Start steam,
start source sdk
start hammer

recently i made a shortcut to hammer on my desktop. Now, after starting steam, I simply start hammer. It does not load the sourcesdk, but hammer loads up a lot faster. No change in performance that I noticed other than not having the sdk launcher running, which i guess saves a few.

Anyways, hope it benefits anyone.

The same works for the Model Viewer.

Although you need to have VPROJECT set and you can dynamically change between mods as you can at the bottom of the SDK menu.