I use a 2 man tent from Mountain Hardware (Drifter 2) that packs down nice and small and a sleeping bag (mummy style) for summer that does as well. I use a self inflating sleep pad by Therma Rest that has been doing it's job for years now. I recently bought a self inflating pillow that makes camping much more comfortable for about $10.
In the States check out REI.
Camping and hiking gear, tents, sleeping bags from REI
Generally speaking buy a sleeping bag rated for 20 degrees cooler than what you actually expect to normally use it for. I have a Summer bag and a Spring & Fall bag that is incredibly warm down to -20C. But then I camp a lot!
It all fits in a 25L dry-bag by Outdoor Research that I attach with a 1" (by 8')ratchet strap.
Dry Bag:
http://www.rei.com/product/848362/outdoor-research-ultralight-dry-sack#specsTab
Tent:
Drifter? 2 DP | MountainHardwear.ca
REI Tent:
http://www.rei.com/product/731378/rei-camp-dome-2-tent
A good 2 season tent. The smaller and lighter the more expensive.
Summer Bag at REI:
http://www.rei.com/product/846001/marmot-nanowave-sleeping-bag#reviewsTab
Don't cheap out on the tent or bag, unless you want to be packing heavy and being miserable if the weather craps out.
Other tips from an experienced camper: Don't pack cotton jeans or shirts they take up too much space and are heavy, this is especially true for items like towels. A couple of micro fiber cloths from the automotive store work just as well for drying you off and dry fast and pack light. A pair of hiking pants (that the legs zip off) save packing pants and shorts and save space and weight.
Pack some light weight shoes for after the days ride. I use rafting shoes since they are extremely light and pack much flatter than runners. They still look OK if you want to go into a restaurant or the like vs say "flip-flops". Pack something like a micro-fleece sweater instead of a cotton hoodie since they are so much lighter and easier to pack. If it is a cool evening around the camp fire you can always use your bike jacket to stay warm.
Finally don't forget your rain gear, and keep them easy to get to.