I've submitted my resume to countless employers that say "thank you for your interest, we will contact you within the next two weeks if we want to schedule an interview" etc. while I am waiting and not hearing from them is it okay to check in just to let them know I am very interested?

I first care little about what is "expected" sometimes depending on the job, being aggressive, standing out gets you a job.

I used to do everything I was told not to do, and guess what I had better luck than average.
I make my resume into a 5 X 8 book form Now with that I was applying for jobs that required you to be creatitive and think outside of the box.

I would call them and let them know it was coming, call to see if they got it, and then call about a week latter to see if I could schedle time to come in. Also I would see if I knew anyone there, and try and see if they could say a good word.

Ok if you are trying for the fry cook job at Wend's, maybe not what you need to do, and maybe not what IBM would do, but then it was me and who I was,

In today's job market you have to stand out ( maybe not as much as I did) but you need to go after it and sell yourself

It's true that you really do need to sell yourself. When applying for jobs, it's a good idea to do some research on a company and mention some things that you know about them in your cover letter. Also, it's a good idea to send hand-written thank you cards after an interview and also follow-up calls after submitting information and/or after interviews.

Thank you. Yes, I always send thank you letters after interviews but my question is about the before part of the interview since that's where I'm puzzled. So, I guess it's okay to be persistent? When I'm told to wait for an interview I just want to call and check in during the meantime athough some job postings say 'no phone calls please' and I don't want to be seen as pushy or obnoxious...