allGenreGamer ----> (What kind of games are you talking about? Computer, PS 1/2 or board games? Me, I love Diablo, Quake and Dungeons and Dragons...) I haven't got a dictionary with me, so...oh wait, yes I do. Speech: "A talk or public address." Seminar: "A meeting designed for instruction or education on an idea/topic/issue." In my own words, I think the difference is that with a seminar, you have the freedom to let your expert knowledge of the particular reading shine - feel free to use technical language (this comes in really handy when, for example, talking about specific language techniques in the play, Elizabethan times, the various versions of the King Lear text) and to spend the full amount of time addressing your topic (no need to throw in anecdotes, spend time explaining what each and every term you use means or recapping the plot / themes / characters for the ignorant). To put it another way, the main difference is the audience - the audience at your seminar have come to hear your ideas about King Lear, so you don't have to worry trying to make it interesting / appealing to a broad / mass audience - they will already find it a fascinating topic (otherwise they wouldn't have bothered attending) and have some background knowledge. Be very glad you got to write a seminar - this is basically the teacher saying "get up and tell me absolutely everything you know about a _____ reading", so spew out ALL your ideas (read everything about Lear you can get your hands on so you have heaps of these), just in an organized fashion (think of it as a verbal essay on the reading).
Sorry, I didn't pick a psychological reading (isn't it psychoanalytic?), but my advice would be to search all the notes on this site, plus look at all the old pages in the Advanced forum (this is a goldmine of resources), any online Shakespeare notes pages (eg Sparknotes.com, ClassicNotes), get your hands on as many crib books as possible (buy em or borrow em), consult your class notes, and ask your teacher. Also, if you live anywhere near Macquarie Uni, this has a really comprehensive Shakespeare section, and I mean really - in excess of 500 books on Lear alone! (You can search their catalogue online to cut down on the amount of time you have to spend in the actual building...just make sure to bring lots of photocopying money.)
Hope this helps! (And it should, I'm 1/132 for English, beating all the 4U girls...)