Ridgerunner offered a lot of good points! Re: the clogged vent from foaming contents - if you want to cook beans or dried peas, add a tablespoon or two of cooking oil to help keep down the foaming.
I have a 4 qt. Presto stainless steel pressure cooker and I am mainly cooking for 1-3 people and I make food for my little poodle too. My mom cooked for many, many years with her Presto and never had an accident. Pressure cookers are very safe to use and the "new generation" cookers have many extra features that make them safer and easier to use.
Get a stainless steel model! Easy to clean and no staining. If I were buying again, I would get a 6 qt. cooker - much better for small household cooking I think.
Presto is a good brand, good price - Mirro.....not so much. Fagor is also a good brand, more $$$. Kuhn Rikon is good and even more $$$$.
Presto has the "jiggle" top weighted gauge; Fagor and Kuhn have pop-up indicators for the pressure. Don't be impressed about two pressure cooking (1 and 2 or high and low) - you only really need to cook on high pressure.
A pressure canner needs to be much larger in size to correctly can. I would get
both a 6 qt. cooker
and a large canner. Don't try to both can and cook in the same pot. My 4 qt. stainless Presto was about $50 five years ago or so. Worth every penny.
edit: I would caution against an automatic electric (plug-in) pressure cooker. On the Yahoo Group for pressure cooking, lots of folks were convinced these were a no brainer, but this kind of cooker had way more problems than the stove top brands.
I'll be happy to share recipes and further help if you want.
Teresa
A good web site for the Presto:
http://www.pressurecooker-outlet.com/