The Big Laramie River starts at Chambers Lake/reservoir just off CO 14 near the head of the Poudre Canyon, and flows north.
It offers a couple mild May-early June whitewater runs (I to II+) just north of the Colorado line, with 3-4 miles of mellow meanders between. The upper run is hard to access (obscure rutted bouldery vehicle-buggering road, or a steep carry down), for about 3 miles of II rocky rapids and then easy meanders (through private land with low bridges and possible fences). Fishing so-so.
The lower run starts at the WY G&F Jelm Valley Public Fishing area and ends at Woods Landing: I-II about 3 miles, with closely-spaced rocks. At high water, canoeists get spooked on both runs (leaving their craft on the banks and hiking out). But it's fun in duckies and small-medium rafts or cats. The take-out, just above the Hwy. 10 bridge, is at the Woods Landing Resort: beer, burgers, steaks, and western atmosphere to the max.
I live in sight of the Jelm put-in, and am usually good for a shuttle (bring excellent beer).