Pennsylvania
West: Unless an incumbent retires (and so far only Murtha has hinted at that... and thanks to the '02 gerrymandering there's no way the Dems can lose that district) it'll take a strong/star candidate to make any district there competative... talking of which there's a possibility that Heinz will run against Hart in PA-4. Unless there's a sizeable trend against the GOP I'd be suprised if she lost, but as it would generate a lot of media attention, weird things *could* happen.
Central and North East: Kanjorski's hinted that he might retire; under the old lines the district would have been fairly competative, but the addition of Scranton in the '02 gerrymander makes a repeat of 1980 very unlikely.
Other than that...
South East: The award for "Congressman most likely to be job hunting after 2006" goes to Gerlach. If an incumbent comes very close to losing to an underfunded nobody, that incumbent is in serious trouble.
As for Schwartz, Dent and Fitzpatrick... it really depends what sort of record they build up in Congress (both votes and constituency work). It's too early to tell right now.
A district that could be interesting is Weldon's if he retires: it's over 60% Republican but voted for Kerry (I think so anyways) last year and had a Democratic congressman in the late '70's and early '80's.
Schwartz (D-13) and Dent (R-15) will probably go nowhere. Look for Gerlach (R-6) and Fitzpatrick (R-8) as potential job hunters come 2006. I know Schwartz has an incredible staff and she did write to our local paper already about how glad she is to serve us (touchy). You are also right about Weldon's seat. A lot of those 60% are RINOs who vote Dem other than Weldon anyway.