Baskets are more convenient for errands. I live in Japan, where bikes are used more for practical reasons than sport or exercise. Almost 100% go with baskets. Google mamachari if you're interested... You can buy a cheap net for your basket to prevent anything from flying out.

http://www.amazon.com/Sunlite-Bicycle-Bungie-Cargo-Black/dp/B000WY6ZXA

For long commutes, it may depend on the amount of weight.

Just about any bike shop should carry a bungee net thingy that's specifically sized and designed for strapping stuff onto a bike rack. They're quite secure and cost like $10.

Like so.

Sure thing,


The rack is a JANDD Standard rear rack:


https://www.amazon.com/Jandd-Standard-Rear-Rack-Black/dp/B000VSFI76

And the netting is similar to this:


https://www.amazon.com/dp/B000WY6ZXA/ref=asc_df_B000WY6ZXA5085897/?tag=hyprod-20&creative=395033&creativeASIN=B000WY6ZXA&linkCode=df0&hvadid=193154321880&hvpos=1o2&hvnetw=g&hvrand=4001830713657135826&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9058761&hvtargid=pla-310856335170




I can't find the exact brand as i got it in an LBS and I didn't pick it out per ce, i explained what i needed, and the dude just went into the back and slapped this on the bike, lol

Is this same one? cassavetes' seems to have a much thicker shock cord, has four instead of five grids, and has four thick red plastic hooks instead of the six wire ones on the Topeak.

Both are good, but they don't look the same to me.

Edit:

Linky time!

• Heavy duty 15" cargo net
  
  
• Sunlite bungee cargo net
  
  
• Minimal design
  
  
• Delta cargo net
  
  
• Finally - the winner(?) Delta Cycle Megarack Cargo Net. Four large red hooks? Check. Grid size of four? Check. Thick shock cord? Check. $7 price tag? Check.
  
  
• Even cheaper here

I agree--love my cargo net, and got it from Amazon for less than $5:
http://www.amazon.com/gp/product/B000WY6ZXA/ref=as_li_ss_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B000WY6ZXA&linkCode=as2&tag=xoxoadrienn-20

I can strap my backpack on, or take it a step further by using the cargo net to secure a small woven trash basket to the back rack to carry things. My husband does the same with a crate: http://25.media.tumblr.com/tumblr_m6mx77QJzX1qz8fbvo1_500.jpg

As someone who commutes to work on a bike, here's my list. Granted, a few of these don't really apply to mountain biking.

Safety

• Helmet (Keep your head in one piece)
  
• Headlight (See where you're going)
  
• Taillight (Be seen from behind)
  
  

  Security
  

• U-lock (Keep your bike frame)
  
• Axle locks (Keep your wheels)
  
• Saddle lock (Keep your seat)
  
  

  Comfort
  

• Gloves (Pad your hands, keep them warm)
  
• Merino wool layers (Keep you warm, dry and not stinky)
  
• Padded shorts/pants (Pad your bottom)
  
  

  Utility
  

• Rear rack (Carry stuff on your bike, not on your back)
  
• Cargo net (Strap stuff to that rack)
  
• Paniers (Clip large bag of stuff to that rack)

I'm leaving on my Chicago to Seattle Tour on 6/3.

Nashbar makes nice inexpensive panniers. Ortliebs are great but double the cost.

With a handlebar bag or top tube bag you should be able to get away with no front panniers. That means you will have your tent, sleeping bag, and sleeping pad strapped to the top of your rear rack. Try a cargo net: http://www.amazon.com/Pyramid-Bicycle-Bungie-Cargo-Black/dp/B000WY6ZXA/ref=sr_1_1?ie=UTF8&qid=1370021844&sr=8-1&keywords=bicycle+cargo+net

Sleeping pad is a must. Therm-a-rest is ideal but a walmart special will be fine.

I would avoid a rigid attachment as it will likely fail. What about some kind of elastic net that it could fit into? Like a mini cargo-net?

Sunlite Bungee Cargo Net https://www.amazon.com/dp/B000WY6ZXA/ref=cm_sw_r_cp_api_CwuyzbBQ1TEG3

You could mount this to the ceiling.

Not sure what your ceiling looks like now, this will surely force you to put holes in the ceiling material. Don't go through the roof.

My commute is about 11 miles there and back - I keep all my things in a backpack that I secure to my rack trunk with this bungee net. It works like a charm for irregularly shaped items like the various coffee paraphernalia you mentioned. I would suggest grinding your coffee in the morning and taking it in a mason jar or something - after a few trips to and from work you will want to lighten your load as much as possible. If you can keep an electric kettle at work, that would be optimal. If not, then probably just microwave your water.