Empty wine bladders can be used either on their own (when slightly blown up are visually interesting and feel good to baby) or you can put dried rice or small past in them to make noise.
You can also make your own mobiles and hang things like shiny CD's, stretchy ribbons, bangles ect off them and change items on them to keep baby interested.
Teething toys are also good at this age and can keep bubs busy for some time. Um, what else......... You could use lids from milk containers and string them together (need to put hole in lid) and link them to make a long shaker (similar idea to what you would buy but make it instead to save expense).

Will let you know if I think of more. :-k