[on_dope]

I simply agree with Moonlight , re-phrase your mail everytime coz you never know who all would be in the selection committee. SOP is read only by the graduate selection commitee(graduate school selection committe is different from selection committe of individual departments) or it may also be read by the interviewer ( who may be from your department )initially to know abt you and take your interview. anyway
starting format of such request letter can be like

"I am really delighted at being offered admission to the Masters in ABC program at your esteemed University.
HoweverI will need substantial financial aid to fund my education through work-study programs.I have over abcdef months of full time work experience in the Computers & IT field - in a rapidly evolving and increasingly competitive
business environment that .................................................. "

just make a paragraph about what all you have that you can give to them & then in the later sections of para do mention that you have worked with such such orgranizations( its repetetive coz you'd b attaching your resume still its always wise to mention it coz if by chance their eyes catches a glimpse of the names & eventually out of curiousity they may open your resume too )