I use Bachman's care sheet for seed starting times. The weekly update is also helpful. I like to read the archives.
http://www.bachmans.com/retail/gardening/weekly_updates_index.cfm

Here is a link that might be useful: Indoor Seed Starting Calendar

Hi mnlamb. I wouldn't bother with sqash, cucumbers, beans, or peas. They all grow really fast and should generally have the seeds planted right in the garden. Possibly the same for beets as I've never seen seedlings sold for root plants like beets or carrots or parsnips.

Kohlrabi could definitely be started indoors as well as cabbage, cauliflower, broccoli, and brussel sprouts.

Onions and okra can be started indoors.

Here's my favorite site for finding out WHEN each kind of seed should be started.

Herbs can be started indoors as well.

Here is a link that might be useful: When to plant?