What is the point of carrying all the junk that you find in Fallout 3?

I'm finally playing fallout 3 and I find myself burdened with junk. Lawnmower blades, vacuum cleaners, sensor modules, scrap metal, etc. Should I continue to carry all these? My brief survey of crafting blueprints seems to indicate that there is a distinct limit on how much you can do in the building department. Should I instead just sell everything that I get or is there a point in hoarding some of this stuff?

Will it ever be useful to fix my weapons? or are there other things I can do with them?

Later in the game you will acquire weapon schematics which specify these parts. ie. you will be able to make weapons out of them.

While there's little point hoarding hundreds of each item, you will find it useful to make multiple copies of each weapon since that lets you repair them when they deteriorate. So it's useful to hang on to some of the junk. The rest you could sell.

See here if you want to see the weapons you can make and what parts you need to make them.

Rock-It launcher

Until you've dismembered a Feral Ghoul with a high-velocity FTB* round, you haven't really played F3.

*Fluffy Teddy Bear

There is more of a point to hoarding random stuff in New Vegas. Really, for convenience, in Fallout 3 I sold all the expensive stuff and secreted ten copies of each of the useful things for weapons blueprints (you do find some more throughout the game--the flaming sword and bottlecap mine are spectacular with the right perks) for later use.

You are not going to face any significant difficulty at all if you simply sell all of these things.

There is no point of carrying them around. Leave them in a locker in your house, use them when you get schematics.