Does anyone have recommendations for reputable plant and seed catalogs, for northern climates? I’m in zone 4, and it seems that everything that catches my eye requires warmer locations.
Park Seed (http://www.parkseed.com) - enter “Zone 4” in the search box and you’re good to go.
I can’t guarantee what catches your eye. 
There’s a few factors at play here with seeds. Often, retail seed outlets get their seed from various seed brokers, so, even if they have a Northern address, the seeds may come from different suppliers, not neccessarily grown in that climate.
I think more what you’re asking is seed companies that sell seed of plants that are proven to do well in Northern climates. One that wasn’t mentioned in Harmonious Discord’s list is a fine Maine seed company is Johnny’s Selected Seeds. They have a really informative catalog, geared to Northern gardeners.
Last year Jung’s was bragging that the founder bred some varieties of asters while listing a certain variety of extreme pride to them. The irony was they didn’t have the variety for sale. You would expect something of such pride to be sold and maintained by them wouldn’t you? I know they are still a family owned business too, because they are based in my dads home town. The place used to grow all it’s own seeds in that town except for a couple imports. They switched the corn seed production to a more southern state in the 80’s or 90’s. I believe. You can still see the flower fields if you drive around. There was some huge melt down in the late 80’s early 90’s of many of the seed companies with a result that many varieties were dropped.
I’d forgotten about Johnny’s Select Seeds. Last year I started to remember the companies I used to get catalogs from and Johnny’s was one of them.
Gurney’s always had good prices as did Jung’s.
Park’s is expensive, but has always had some very unique varieties, so if unique is more important than price try them.
Johnny’s is pretty good but has gotten kind of pricey. Pinetree Garden Seeds is also based in Maine and offers small-size packets (usable amounts) for considerably less than many other seed houses). Their shipping has gone up quite a bit though.
There’s Vermont Bean Seed Company (which I haven’t dealt with) and major seed houses like Park’s and Burpee. Park’s was fine for many years but has started to get poor consumer ratings on the Garden Watchdog, which they had had for non-seed items but are starting to get for seeds as well. This is the first year in many that I haven’t ordered from them.
J.L. Hudson Seeds is based in California but has lots of annuals and perennials that do well in colder climates. Their catalog is also a gas, as the owner is evidently somewhere between a libertarian and an anarchist, and likes to share his political views.
One more - The Fragrant Path is a small seed house in Nebraska, and pays attention to hardiness in its selections (a lot of them but not all are of plants with fragrant flowers and leaves).
Renee’s Garden is a very nice smaller seed company.
Henry Feild’s has been around along time.
Here’s a nice listing of U.S. and Canadian seed companies from the Mother Earth News. There’s an annoying subscription pop-up when you click onto the site, but the article has seed companies listed by state and then lumps all the Canadian ones together. The web sites may tell you whether they ship to your location or whether the seeds will be happy where you are. The article also links to a seed and plant finder.