There are lots of ways to accomplish your wish - here is what I do.
I assume you have a photo editor of some kind that resizes pics? I think I have 3-4 of them on my pc, but currently am using PaintShop Pro XI. All digitial cameras also come with one. Microsoft Office has a Photo Editor. Even Windows Vista can do some editing. Lots and lots of other options too. Anyway - in the menu you should have an option for each photo that you open for editing that says "resizing". I find 800X600 works well (or something similar). After resizing I "save as" the same name as the original except add a suffix "a" to the end - this tells me that it is the saved smaller version of the pic for quickly going through posting or placing in emails and such later. I keep the larger version available for printing or other editing purposes at a later date.
If you want thumbnails you just select the paperclip and upload the "a" version. If you want the larger photos (also the "a" version) in your posts then you first upload to a repository like photobucket.com (which I use and find a good place) and then when you select the mountain icon you insert the http address where your pic is stored for attachment purposes (within photobuckst or other).
With a little practice you will have it down pat in no time! Looking forward to LOTS of pics.........
mike