i have the rick steves bag
100 bucks
on his website: www.ricksteves.com
a relatively compact bag that fits on a plane as carry on!

How big are we talking here?  Are you male or female?

That bag is nice.  EBags has one that is just like it but more zippers and such.  Very nice bag for half the price.

My wife and I both purchased bags last month from MEC (Mountain Equipment Co). They are great…
 
MEC Sojourn Travel Pack
http://www.mec.ca/Products/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524442096519&FOLDER%3C%3Efolder_id=2534374302883912&bmUID=1184620422190
 
We are planning a month in Europe, and doing quite a bit of flying. We will check this bag and carry the detachable daypack. the bext think is that all the straps on this bag zip inside and you can attach a shoulder strap. Preventing damage from convayer belts…
B

i also have a MEC Sojourn
it’s too big to carry on a plane though
not as comfortable as the real hiking packs although better zipper system
i still use the front pack as my day pack
i bought the rick steves bag because i don’t trust airlines from losing my stuff and for needing to wait a long time if they do lose it wondering……where’s my bag?

I have an old Eagle Creek bag from 1997.  Its still in excellent shape and is a great size at only 3200 cubic inches.  So check out used Eagle Creek bags on Ebay.  Another good choice is the Osprey Porter series bags.  Those are also great travel bags and very small like you are looking for.   

A couple of packs on clearance at REI for under $100:
Adjustable unisex pack (probably not a good choice if you’re a short woman or tall guy):
http://www.rei.com/online/store/ProductDisplay?productId=48044169

Women’s pack: http://www.rei.com/REI-Outlet/product/745609

This is the one I bought.  Very similar to the one Rick Steves is selling.
 
http://www.ebags.com/ebags/weekender_convertible/product_detail/index.cfm?modelid=15026
 
 

http://www.campmor.com/webapp/wcs/stores/servlet/ProductDisplay?productId=39302353&memberId=12500226&storeId=226&catalogId=40000000226&langId=-1
 
I just got back from a 3 1/2 week backpacking trip through Europe and this is the pack I got and I liked it very much.

I am a female. I don’t know exactly what size I’m looking for really. Thank all of you for your responses. I like the look of the Osprey bag. I may go for that one unless anyone has any better suggestions. Thanks!

Osprey does make good packs, so you probably can’t go wrong with it.  I like the features of that REI pack I posted – detachable daypack, zip-away straps for when you check it for your flight,  panel-loading, and a security cable so you can lock the pack to something.  It’s not the best color, but for the features and quality it’s a great deal.

Hi, I’m going backpacking through Europe for the first time for just over 1 month and don’t know how large of a bag I should buy. I’ve been looking at bags that are around 2600 cubic inches and bringing a regular backpack as well? Does this sound too small? I’ve seen some as large as 3500 cubic inches and don’t know if that would be going overboard. I’ll be traveling a lot and staying in hostels, so I don’t want something that will be dificult on the trains. I’ve posted one that I’ve been looking at, any comments? Any advice would be greatly appreciated.
 
http://www.altrec.com/shop/detail/28211/

2600 cubic inches (44l) is by no means large.  I’d have to pack really light to get by with that, but think I could pll it off.  3500 is getting to the larger end of the spectrum, but you’d have zero trouble on trains and in hostels.  I’ve travelled quite a bit with a pack that was about 4000 cubic inches and it wasn’t any problem, and it allowed me to have room for stuff I wanted to bring back with me.  Packs designed for backpack travel can be nice – panel loading (it unzips on the side so you don’t have to dig through everything to get to stuff at the bottom), detachable daypacks, zip away straps for when you check it on the plane – but a top-loading pack is fine too.  Making sure your pack fits and won’t fall apart on you are the most important things.  If you can, visit a local store and get fitted for a pack and try on various models.  You can then look for a better price online.