I must be odd, because I DO recall the small things from some weddings- matching invitation colours to the table decorations etc.
I DIY'd multiple things. I found a company to print the basic invite, but I hole punched and added ribbon/embellishments. The envelopes came flat packed and needed sticking together. They came out better than any I'd seen from a regular stationers and cost about 1/3.
I did look at vistaprint, but found that the earlier you order, the cheaper it was, and I'd run out of time to get any savings.
We printed thank you cards at home, using photos from the wedding as the card. I also had some photos printed of the guests, so each thank you card included at least 1 printed photo of that guest.
I'd bought cake/favour bags from poundland. They were made of card and in the shape of a bride and groom- they were 10p each! I then made the favours myself. I melted chocolate then added coconut, cherries, mixed fruit or nuts and put them into heart shaped moulds. None were left on the tables.
The only things I regret was making pew ends. They ended up looking like floppy ribbons and were a waste of money/time.
Chair covers is another waste, unless the chairs are absolutely dire. People will leave their bags/coats etc on the chairs so you don't see them anyways. I hired mine, but wish I hadn't bothered.