Gloop - STOP GROVELING - there are plenty of companies out there that would snap off the hand of a good employee - are you that person - other answers are right - do your homework first - make the cover letter personal - look up some key facts of the company and keep a list of all you apply to - you will soon need this information once you get a grip with your self - I get the impression from your Q that your heart skips a beat every time you post a letter or e-mail off and every time your phone rings ( just incase it's the company calling you) - don't be so nervous - stand in the mirror and tell your self you are worthy of the job you seek and translate that to the words you use in your letter - this in turn will produce interest from the reader and you will get a reply - be confident remember they are now seeking your expertise - this will then translate it's self to a confident and intellegent employee and the company will soon be putting YOU forward for promotion
A friend who once sent companies a piece of wrapped bread and butter explaining that they had the makings of a good sandwhich the next day she sent another piece telling them that all they needed was the best filling ever - the jam that kept the two halves together - if they wanted the "Jam " they should ring her soon before someone else uses it for their sandwich - she was not unemployed for long - Now I'm not suggesting you go this far but look over your Question again and see how many negatives and submisive comments there are in it and ask your self why would a company want me in this mode. I also get the impression that you are very young - young is good, new blood, new ideas, once you have done your "homework" with these companies only apply to the ones that will suit you and your style of work - and remember good companies NEED good employees THATS YOU - They need YOU!!
I won't say good luck you won't need it - but all the best when it comes to choosing which one you