the section of the thames path i did with jim (west to richmond on the south side) is a joke its true but greenwich to dartford, also on the southbank is fantastic. i well reccommend it. i want to go further next time, into jencks territory, leigh-on-sea sort of thing.
i find a lot of the canals are too crowded and the bridges are a real pain. worst of all are the commuters trying to sho how fast they can go, towpaths not the best place for a time trial in my opinion. limehouse cut is usually alright but regents canal, particularly in rush hour is nightmarish. they're alright after dark though. someone i know did actually get pushed into the canal there. wiles disease awaits... i do want to make it up to little venice some time though.
if you do the greenway make sure to surmount beckton alp but watch out for all the broken glass. they've also fucked up the little dirtbike trail with mechanical diggers which is a bit kiljoyish, i like scaring myself there.
i like epping forest, its a laugh so long as the mud hasn't got too bad. eastway cycle track is fun too. i used to go there as a boy back when the world was all in black and white and playstations didn't exist.
greenwich foot tunnel i always push my bike for the sense of moral superiority it provides.
lea naviagtion hackney to waltham abbey is good, then a ride around lea valley park. i worked out a nice one where you go through near enough the whole of epping forest then join the lea navigation back home.
the old railway line i think works better as a walk as its so short but its a great place to visit.