I don't know a good article I could point you to any better than yourself doing a web search, but I would first recommend that a good understanding begins with learning plant families and how each family tends to reproduce.

For example... does the plant family have what are called 'perfect flowers'? Do they generally have separate 'male' and 'female' flowers that require a vector to transfer pollen.

Then, if cross-pollination becomes a concern, a good understanding about choosing to grow more than one variety from any particular plant family, and if you do... how to protect variety crosses (unless it's purposeful) with such techniques as bagging, or even 'safe proximity'.

For plant families which easily cross-pollinate, you can do what I call... rotated flowering. One year, let your broccoli go to seed. The next year let your cauliflower bloom. Etc...

For detail, keep asking here, or search around the web. I use a fairly well-trusted seed source, and they have a very knowledgeable phone support for the basic questions concerning their varieties.

Different varieties of the same species will cross with each other. To what extent depends on the type of plant. Something labeled as an "heirloom" is not exempt from this. To keep an heirloom true to type you must prevent any crossing whatsoever.

http://www.seedsave.org/issi/issi_904.html

That link should give you good start in regards to saving seeds from the common veggies. You might also want to check the FAQ on this forum.

Rodney

http://faq.gardenweb.com/discussions/2766772/how-do-i-prevent-tomatoes-from-cross-pollinating

And there's a very detailed page from the FAQ on the Tomato Forum.

Rodney