If your training the right way like you would for an IM then weight training isnt going to add 'bulk' like some people think it will. There have a been some great posts here recently on weight training as were all approaching the dreaded off season. Youll find some great threads with a little bit of search engine use. Good luck!!

I usually have to do a trainer ride before work in the am twice a week and this is when i
like to do my free weight training also. I also have a chinup bar that i use this not only for
upperbody but abs too. My arms look pretty good for a woman except for my veins that
pop too much especially by the end of the day!

I have found strength training to be really helpful to build solid foundations in those support muscles that do the work in the swim, bike and run - especially for the longer distance stuff. Without buidling up those muscles a bit injury is far more likely. Proof of that is my patellar tracking issues that I dealt with leading up to IMCDA which I'm sure are a result of slacking off in my quad strength exercises...now that I've incoprorated them back in....no issues!

Anyway, a program with some shoulder stuff, some quad and ham stuff, and a big focus on core stuff will be good. As toothless says, you don't want to kill yourself in the weight room, but consistency is key to ensure that those foudation muscles will get stronger. Maybe shoot for 2X/week as mentioned above and about :30 - :45 minutes each session....

What the literature says for endurance athletes is to do strength training two times a week, low weights, high reps(15-20-30 reps); body weight excercises are great, plyometric or circuit routines will do too. There is no way you´ll turn into a bodybuilder body with that regimen.
The key is to build muscle endurance.

I focus on legs, shoulders, back, and core in the gym. I try to superset 3 exercises in a row for each followed by 3 sets of abs/lower back. For ex. I start with leg extensions, leg presses, lunges then right into 3 core movements. Repeat 3 times, then on to shoulders. This way I get 9 sets for the major bodyparts and 27 for core.

I also do pushups, with varying arm positions at home and at the track. I like to end my speedwork sessions with a the goal of doing a 7:00 minute mile with 50 pushups at the end of each 400 (I stop the watch while doing the pushups).

I do 2 x a week, usually at home with bodyweight + hand weights. The usual stuff: squats, lunges, crunches, reverse crunches on an exercise ball, pushups, curls, triceps extensions. I also do karate 3x a week, and that involves some of this stuff, plus deep stances that work the legs, glutes, and abs.